diff --git a/STYLE_GUIDE.md b/STYLE_GUIDE.md
index 3e466bf8e..c9887527c 100644
--- a/STYLE_GUIDE.md
+++ b/STYLE_GUIDE.md
@@ -177,7 +177,7 @@
 
 ## Standards
 
-- OpenThread uses and enforces both Python 2 and Python 3.  Support for Python 2 is a result of the fact that some current Linux distributions and Macs are still using 2.x as default.
+- OpenThread uses and enforces Python 3.
 
 ## Conventions and Best Practices
 
diff --git a/tests/scripts/thread-cert/Cert_5_1_01_RouterAttach.py b/tests/scripts/thread-cert/Cert_5_1_01_RouterAttach.py
index 9cd6eb499..48d0aeac2 100755
--- a/tests/scripts/thread-cert/Cert_5_1_01_RouterAttach.py
+++ b/tests/scripts/thread-cert/Cert_5_1_01_RouterAttach.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_02_ChildAddressTimeout.py b/tests/scripts/thread-cert/Cert_5_1_02_ChildAddressTimeout.py
index eeccbf260..27adb96c8 100755
--- a/tests/scripts/thread-cert/Cert_5_1_02_ChildAddressTimeout.py
+++ b/tests/scripts/thread-cert/Cert_5_1_02_ChildAddressTimeout.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_03_RouterAddressReallocation.py b/tests/scripts/thread-cert/Cert_5_1_03_RouterAddressReallocation.py
index c7dbd4957..8dbb5b540 100755
--- a/tests/scripts/thread-cert/Cert_5_1_03_RouterAddressReallocation.py
+++ b/tests/scripts/thread-cert/Cert_5_1_03_RouterAddressReallocation.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_04_RouterAddressReallocation.py b/tests/scripts/thread-cert/Cert_5_1_04_RouterAddressReallocation.py
index 4cdeaddd7..a94b3f2fc 100755
--- a/tests/scripts/thread-cert/Cert_5_1_04_RouterAddressReallocation.py
+++ b/tests/scripts/thread-cert/Cert_5_1_04_RouterAddressReallocation.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_05_RouterAddressTimeout.py b/tests/scripts/thread-cert/Cert_5_1_05_RouterAddressTimeout.py
index e3aab6603..8d85b4bab 100755
--- a/tests/scripts/thread-cert/Cert_5_1_05_RouterAddressTimeout.py
+++ b/tests/scripts/thread-cert/Cert_5_1_05_RouterAddressTimeout.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_06_RemoveRouterId.py b/tests/scripts/thread-cert/Cert_5_1_06_RemoveRouterId.py
index 030fc4cdf..afd7b3de4 100755
--- a/tests/scripts/thread-cert/Cert_5_1_06_RemoveRouterId.py
+++ b/tests/scripts/thread-cert/Cert_5_1_06_RemoveRouterId.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_07_MaxChildCount.py b/tests/scripts/thread-cert/Cert_5_1_07_MaxChildCount.py
index c625834fe..20c8e8629 100755
--- a/tests/scripts/thread-cert/Cert_5_1_07_MaxChildCount.py
+++ b/tests/scripts/thread-cert/Cert_5_1_07_MaxChildCount.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_08_RouterAttachConnectivity.py b/tests/scripts/thread-cert/Cert_5_1_08_RouterAttachConnectivity.py
index 908b7f70e..08d8627e9 100755
--- a/tests/scripts/thread-cert/Cert_5_1_08_RouterAttachConnectivity.py
+++ b/tests/scripts/thread-cert/Cert_5_1_08_RouterAttachConnectivity.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_09_REEDAttachConnectivity.py b/tests/scripts/thread-cert/Cert_5_1_09_REEDAttachConnectivity.py
index 7e0189331..5c1398c77 100755
--- a/tests/scripts/thread-cert/Cert_5_1_09_REEDAttachConnectivity.py
+++ b/tests/scripts/thread-cert/Cert_5_1_09_REEDAttachConnectivity.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_10_RouterAttachLinkQuality.py b/tests/scripts/thread-cert/Cert_5_1_10_RouterAttachLinkQuality.py
index 743296f13..5f09e2176 100755
--- a/tests/scripts/thread-cert/Cert_5_1_10_RouterAttachLinkQuality.py
+++ b/tests/scripts/thread-cert/Cert_5_1_10_RouterAttachLinkQuality.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_11_REEDAttachLinkQuality.py b/tests/scripts/thread-cert/Cert_5_1_11_REEDAttachLinkQuality.py
index e4dd91330..be6195dd9 100755
--- a/tests/scripts/thread-cert/Cert_5_1_11_REEDAttachLinkQuality.py
+++ b/tests/scripts/thread-cert/Cert_5_1_11_REEDAttachLinkQuality.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_12_NewRouterNeighborSync.py b/tests/scripts/thread-cert/Cert_5_1_12_NewRouterNeighborSync.py
index c7ea1c8dd..738ebd219 100755
--- a/tests/scripts/thread-cert/Cert_5_1_12_NewRouterNeighborSync.py
+++ b/tests/scripts/thread-cert/Cert_5_1_12_NewRouterNeighborSync.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_1_13_RouterReset.py b/tests/scripts/thread-cert/Cert_5_1_13_RouterReset.py
index 6c2952d48..1c5a7a71e 100755
--- a/tests/scripts/thread-cert/Cert_5_1_13_RouterReset.py
+++ b/tests/scripts/thread-cert/Cert_5_1_13_RouterReset.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_2_01_REEDAttach.py b/tests/scripts/thread-cert/Cert_5_2_01_REEDAttach.py
index 0571c220d..3461095cd 100755
--- a/tests/scripts/thread-cert/Cert_5_2_01_REEDAttach.py
+++ b/tests/scripts/thread-cert/Cert_5_2_01_REEDAttach.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_2_03_LeaderReject2Hops.py b/tests/scripts/thread-cert/Cert_5_2_03_LeaderReject2Hops.py
index a28f74aaf..df084f830 100755
--- a/tests/scripts/thread-cert/Cert_5_2_03_LeaderReject2Hops.py
+++ b/tests/scripts/thread-cert/Cert_5_2_03_LeaderReject2Hops.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_2_04_REEDUpgrade.py b/tests/scripts/thread-cert/Cert_5_2_04_REEDUpgrade.py
index ce54fd438..062e97702 100755
--- a/tests/scripts/thread-cert/Cert_5_2_04_REEDUpgrade.py
+++ b/tests/scripts/thread-cert/Cert_5_2_04_REEDUpgrade.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_2_05_AddressQuery.py b/tests/scripts/thread-cert/Cert_5_2_05_AddressQuery.py
index 9efb67442..e4a9e3b38 100755
--- a/tests/scripts/thread-cert/Cert_5_2_05_AddressQuery.py
+++ b/tests/scripts/thread-cert/Cert_5_2_05_AddressQuery.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_2_06_RouterDowngrade.py b/tests/scripts/thread-cert/Cert_5_2_06_RouterDowngrade.py
index 91c6d30c0..963ad7f0c 100755
--- a/tests/scripts/thread-cert/Cert_5_2_06_RouterDowngrade.py
+++ b/tests/scripts/thread-cert/Cert_5_2_06_RouterDowngrade.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_2_07_REEDSynchronization.py b/tests/scripts/thread-cert/Cert_5_2_07_REEDSynchronization.py
index 49315f678..d642e964d 100755
--- a/tests/scripts/thread-cert/Cert_5_2_07_REEDSynchronization.py
+++ b/tests/scripts/thread-cert/Cert_5_2_07_REEDSynchronization.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_01_LinkLocal.py b/tests/scripts/thread-cert/Cert_5_3_01_LinkLocal.py
index 90a90426e..e7f9bd712 100755
--- a/tests/scripts/thread-cert/Cert_5_3_01_LinkLocal.py
+++ b/tests/scripts/thread-cert/Cert_5_3_01_LinkLocal.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_02_RealmLocal.py b/tests/scripts/thread-cert/Cert_5_3_02_RealmLocal.py
index 97452b6e2..f5fd3a103 100755
--- a/tests/scripts/thread-cert/Cert_5_3_02_RealmLocal.py
+++ b/tests/scripts/thread-cert/Cert_5_3_02_RealmLocal.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_03_AddressQuery.py b/tests/scripts/thread-cert/Cert_5_3_03_AddressQuery.py
index 7d438c3f6..ea6e0f4fc 100755
--- a/tests/scripts/thread-cert/Cert_5_3_03_AddressQuery.py
+++ b/tests/scripts/thread-cert/Cert_5_3_03_AddressQuery.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_04_AddressMapCache.py b/tests/scripts/thread-cert/Cert_5_3_04_AddressMapCache.py
index 178bf7666..722ef645e 100755
--- a/tests/scripts/thread-cert/Cert_5_3_04_AddressMapCache.py
+++ b/tests/scripts/thread-cert/Cert_5_3_04_AddressMapCache.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_05_RoutingLinkQuality.py b/tests/scripts/thread-cert/Cert_5_3_05_RoutingLinkQuality.py
index 14a76ae18..af6a1dc0c 100755
--- a/tests/scripts/thread-cert/Cert_5_3_05_RoutingLinkQuality.py
+++ b/tests/scripts/thread-cert/Cert_5_3_05_RoutingLinkQuality.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_06_RouterIdMask.py b/tests/scripts/thread-cert/Cert_5_3_06_RouterIdMask.py
index c62c6bec5..d20379b77 100755
--- a/tests/scripts/thread-cert/Cert_5_3_06_RouterIdMask.py
+++ b/tests/scripts/thread-cert/Cert_5_3_06_RouterIdMask.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_06b_RouterIdMask.py b/tests/scripts/thread-cert/Cert_5_3_06b_RouterIdMask.py
index 08850822e..0403e978f 100755
--- a/tests/scripts/thread-cert/Cert_5_3_06b_RouterIdMask.py
+++ b/tests/scripts/thread-cert/Cert_5_3_06b_RouterIdMask.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_07_DuplicateAddress.py b/tests/scripts/thread-cert/Cert_5_3_07_DuplicateAddress.py
index 7918e21fa..3f65a3766 100755
--- a/tests/scripts/thread-cert/Cert_5_3_07_DuplicateAddress.py
+++ b/tests/scripts/thread-cert/Cert_5_3_07_DuplicateAddress.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_08_ChildAddressSet.py b/tests/scripts/thread-cert/Cert_5_3_08_ChildAddressSet.py
index fa9c25657..4e6b7c4a0 100755
--- a/tests/scripts/thread-cert/Cert_5_3_08_ChildAddressSet.py
+++ b/tests/scripts/thread-cert/Cert_5_3_08_ChildAddressSet.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_09_AddressQuery.py b/tests/scripts/thread-cert/Cert_5_3_09_AddressQuery.py
index 496d127e5..d5b856ccb 100755
--- a/tests/scripts/thread-cert/Cert_5_3_09_AddressQuery.py
+++ b/tests/scripts/thread-cert/Cert_5_3_09_AddressQuery.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_10_AddressQuery.py b/tests/scripts/thread-cert/Cert_5_3_10_AddressQuery.py
index fb576cd87..de8fa3a47 100755
--- a/tests/scripts/thread-cert/Cert_5_3_10_AddressQuery.py
+++ b/tests/scripts/thread-cert/Cert_5_3_10_AddressQuery.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_3_11_AddressQueryTimeoutIntervals.py b/tests/scripts/thread-cert/Cert_5_3_11_AddressQueryTimeoutIntervals.py
index 5db66395d..eb161534b 100755
--- a/tests/scripts/thread-cert/Cert_5_3_11_AddressQueryTimeoutIntervals.py
+++ b/tests/scripts/thread-cert/Cert_5_3_11_AddressQueryTimeoutIntervals.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_5_01_LeaderReboot.py b/tests/scripts/thread-cert/Cert_5_5_01_LeaderReboot.py
index d6bf2a51d..eddb05d10 100755
--- a/tests/scripts/thread-cert/Cert_5_5_01_LeaderReboot.py
+++ b/tests/scripts/thread-cert/Cert_5_5_01_LeaderReboot.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_5_02_LeaderReboot.py b/tests/scripts/thread-cert/Cert_5_5_02_LeaderReboot.py
index 863562963..c911fc55d 100755
--- a/tests/scripts/thread-cert/Cert_5_5_02_LeaderReboot.py
+++ b/tests/scripts/thread-cert/Cert_5_5_02_LeaderReboot.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_5_03_SplitMergeChildren.py b/tests/scripts/thread-cert/Cert_5_5_03_SplitMergeChildren.py
index 8582a5f84..c5c92f42c 100755
--- a/tests/scripts/thread-cert/Cert_5_5_03_SplitMergeChildren.py
+++ b/tests/scripts/thread-cert/Cert_5_5_03_SplitMergeChildren.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_5_04_SplitMergeRouters.py b/tests/scripts/thread-cert/Cert_5_5_04_SplitMergeRouters.py
index e9f081ab5..a9c8aa3a8 100755
--- a/tests/scripts/thread-cert/Cert_5_5_04_SplitMergeRouters.py
+++ b/tests/scripts/thread-cert/Cert_5_5_04_SplitMergeRouters.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_5_05_SplitMergeREED.py b/tests/scripts/thread-cert/Cert_5_5_05_SplitMergeREED.py
index 38e5c27c5..d0930a112 100755
--- a/tests/scripts/thread-cert/Cert_5_5_05_SplitMergeREED.py
+++ b/tests/scripts/thread-cert/Cert_5_5_05_SplitMergeREED.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_5_07_SplitMergeThreeWay.py b/tests/scripts/thread-cert/Cert_5_5_07_SplitMergeThreeWay.py
index 18c2636bc..08ee6a9ec 100755
--- a/tests/scripts/thread-cert/Cert_5_5_07_SplitMergeThreeWay.py
+++ b/tests/scripts/thread-cert/Cert_5_5_07_SplitMergeThreeWay.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_5_08_SplitRoutersLostLeader.py b/tests/scripts/thread-cert/Cert_5_5_08_SplitRoutersLostLeader.py
index f5b92964e..6da034bcd 100755
--- a/tests/scripts/thread-cert/Cert_5_5_08_SplitRoutersLostLeader.py
+++ b/tests/scripts/thread-cert/Cert_5_5_08_SplitRoutersLostLeader.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_6_01_NetworkDataRegisterBeforeAttachLeader.py b/tests/scripts/thread-cert/Cert_5_6_01_NetworkDataRegisterBeforeAttachLeader.py
index 9a261d5a8..5e172e7fe 100755
--- a/tests/scripts/thread-cert/Cert_5_6_01_NetworkDataRegisterBeforeAttachLeader.py
+++ b/tests/scripts/thread-cert/Cert_5_6_01_NetworkDataRegisterBeforeAttachLeader.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_6_02_NetworkDataRegisterBeforeAttachRouter.py b/tests/scripts/thread-cert/Cert_5_6_02_NetworkDataRegisterBeforeAttachRouter.py
index 27b1856cc..c4eb66e65 100755
--- a/tests/scripts/thread-cert/Cert_5_6_02_NetworkDataRegisterBeforeAttachRouter.py
+++ b/tests/scripts/thread-cert/Cert_5_6_02_NetworkDataRegisterBeforeAttachRouter.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_6_03_NetworkDataRegisterAfterAttachLeader.py b/tests/scripts/thread-cert/Cert_5_6_03_NetworkDataRegisterAfterAttachLeader.py
index e75b18276..cbbfe7b65 100755
--- a/tests/scripts/thread-cert/Cert_5_6_03_NetworkDataRegisterAfterAttachLeader.py
+++ b/tests/scripts/thread-cert/Cert_5_6_03_NetworkDataRegisterAfterAttachLeader.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_6_04_NetworkDataRegisterAfterAttachRouter.py b/tests/scripts/thread-cert/Cert_5_6_04_NetworkDataRegisterAfterAttachRouter.py
index c6816d4f2..d7ad91e47 100755
--- a/tests/scripts/thread-cert/Cert_5_6_04_NetworkDataRegisterAfterAttachRouter.py
+++ b/tests/scripts/thread-cert/Cert_5_6_04_NetworkDataRegisterAfterAttachRouter.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_6_05_NetworkDataRegisterAfterAttachRouter.py b/tests/scripts/thread-cert/Cert_5_6_05_NetworkDataRegisterAfterAttachRouter.py
index f868a56fe..18af5ae82 100755
--- a/tests/scripts/thread-cert/Cert_5_6_05_NetworkDataRegisterAfterAttachRouter.py
+++ b/tests/scripts/thread-cert/Cert_5_6_05_NetworkDataRegisterAfterAttachRouter.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_6_06_NetworkDataExpiration.py b/tests/scripts/thread-cert/Cert_5_6_06_NetworkDataExpiration.py
index 340d88d34..0c4de82ae 100755
--- a/tests/scripts/thread-cert/Cert_5_6_06_NetworkDataExpiration.py
+++ b/tests/scripts/thread-cert/Cert_5_6_06_NetworkDataExpiration.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_6_07_NetworkDataRequestREED.py b/tests/scripts/thread-cert/Cert_5_6_07_NetworkDataRequestREED.py
index 03c333222..feb89ad53 100755
--- a/tests/scripts/thread-cert/Cert_5_6_07_NetworkDataRequestREED.py
+++ b/tests/scripts/thread-cert/Cert_5_6_07_NetworkDataRequestREED.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_6_08_ContextManagement.py b/tests/scripts/thread-cert/Cert_5_6_08_ContextManagement.py
index 94f82caa4..ff82c7c32 100755
--- a/tests/scripts/thread-cert/Cert_5_6_08_ContextManagement.py
+++ b/tests/scripts/thread-cert/Cert_5_6_08_ContextManagement.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_6_09_NetworkDataForwarding.py b/tests/scripts/thread-cert/Cert_5_6_09_NetworkDataForwarding.py
index c907b7d00..bf8b4916d 100755
--- a/tests/scripts/thread-cert/Cert_5_6_09_NetworkDataForwarding.py
+++ b/tests/scripts/thread-cert/Cert_5_6_09_NetworkDataForwarding.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_8_01_KeySynchronization.py b/tests/scripts/thread-cert/Cert_5_8_01_KeySynchronization.py
index 4eada6a35..41adbbc01 100755
--- a/tests/scripts/thread-cert/Cert_5_8_01_KeySynchronization.py
+++ b/tests/scripts/thread-cert/Cert_5_8_01_KeySynchronization.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_8_02_KeyIncrement.py b/tests/scripts/thread-cert/Cert_5_8_02_KeyIncrement.py
index 457a000a0..27a4c52bc 100755
--- a/tests/scripts/thread-cert/Cert_5_8_02_KeyIncrement.py
+++ b/tests/scripts/thread-cert/Cert_5_8_02_KeyIncrement.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_5_8_03_KeyIncrementRollOver.py b/tests/scripts/thread-cert/Cert_5_8_03_KeyIncrementRollOver.py
index b97fdfdc4..b70eeb77c 100755
--- a/tests/scripts/thread-cert/Cert_5_8_03_KeyIncrementRollOver.py
+++ b/tests/scripts/thread-cert/Cert_5_8_03_KeyIncrementRollOver.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_1_01_RouterAttach.py b/tests/scripts/thread-cert/Cert_6_1_01_RouterAttach.py
index b5a85fc4e..a812277e6 100755
--- a/tests/scripts/thread-cert/Cert_6_1_01_RouterAttach.py
+++ b/tests/scripts/thread-cert/Cert_6_1_01_RouterAttach.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach_MED.py b/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach_MED.py
index 347a4bece..62440f73d 100755
--- a/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach_MED.py
+++ b/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach_MED.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach_SED.py b/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach_SED.py
index b3f47e8b6..41d588206 100755
--- a/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach_SED.py
+++ b/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach_SED.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_1_03_RouterAttachConnectivity.py b/tests/scripts/thread-cert/Cert_6_1_03_RouterAttachConnectivity.py
index f0a61eb07..eebb4e312 100755
--- a/tests/scripts/thread-cert/Cert_6_1_03_RouterAttachConnectivity.py
+++ b/tests/scripts/thread-cert/Cert_6_1_03_RouterAttachConnectivity.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_1_04_REEDAttachConnectivity.py b/tests/scripts/thread-cert/Cert_6_1_04_REEDAttachConnectivity.py
index 2a7a6690a..c2ee061ae 100755
--- a/tests/scripts/thread-cert/Cert_6_1_04_REEDAttachConnectivity.py
+++ b/tests/scripts/thread-cert/Cert_6_1_04_REEDAttachConnectivity.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_1_05_RouterAttachLinkQuality.py b/tests/scripts/thread-cert/Cert_6_1_05_RouterAttachLinkQuality.py
index b9b812ca1..7f3311832 100755
--- a/tests/scripts/thread-cert/Cert_6_1_05_RouterAttachLinkQuality.py
+++ b/tests/scripts/thread-cert/Cert_6_1_05_RouterAttachLinkQuality.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality_ED.py b/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality_ED.py
index 86e930d3c..90661e6a1 100755
--- a/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality_ED.py
+++ b/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality_ED.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality_SED.py b/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality_SED.py
index 21dee6866..8ed653305 100755
--- a/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality_SED.py
+++ b/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality_SED.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_1_07_EDSynchronization.py b/tests/scripts/thread-cert/Cert_6_1_07_EDSynchronization.py
index 69ea8b0d2..6af3b3332 100755
--- a/tests/scripts/thread-cert/Cert_6_1_07_EDSynchronization.py
+++ b/tests/scripts/thread-cert/Cert_6_1_07_EDSynchronization.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_2_01_NewPartition.py b/tests/scripts/thread-cert/Cert_6_2_01_NewPartition.py
index 631f02150..0bfafa6b2 100755
--- a/tests/scripts/thread-cert/Cert_6_2_01_NewPartition.py
+++ b/tests/scripts/thread-cert/Cert_6_2_01_NewPartition.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_2_02_NewPartition.py b/tests/scripts/thread-cert/Cert_6_2_02_NewPartition.py
index c7337d1b9..d2c7cfccf 100755
--- a/tests/scripts/thread-cert/Cert_6_2_02_NewPartition.py
+++ b/tests/scripts/thread-cert/Cert_6_2_02_NewPartition.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_3_01_OrphanReattach.py b/tests/scripts/thread-cert/Cert_6_3_01_OrphanReattach.py
index c3a8e6617..0e7743f23 100755
--- a/tests/scripts/thread-cert/Cert_6_3_01_OrphanReattach.py
+++ b/tests/scripts/thread-cert/Cert_6_3_01_OrphanReattach.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_3_02_NetworkDataUpdate.py b/tests/scripts/thread-cert/Cert_6_3_02_NetworkDataUpdate.py
index d51bfa63f..02b34eae6 100755
--- a/tests/scripts/thread-cert/Cert_6_3_02_NetworkDataUpdate.py
+++ b/tests/scripts/thread-cert/Cert_6_3_02_NetworkDataUpdate.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_4_01_LinkLocal.py b/tests/scripts/thread-cert/Cert_6_4_01_LinkLocal.py
index f759d07e9..1448293cd 100755
--- a/tests/scripts/thread-cert/Cert_6_4_01_LinkLocal.py
+++ b/tests/scripts/thread-cert/Cert_6_4_01_LinkLocal.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_4_02_RealmLocal.py b/tests/scripts/thread-cert/Cert_6_4_02_RealmLocal.py
index 254704ae3..a8bf7a5b7 100755
--- a/tests/scripts/thread-cert/Cert_6_4_02_RealmLocal.py
+++ b/tests/scripts/thread-cert/Cert_6_4_02_RealmLocal.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_5_01_ChildResetSynchronize.py b/tests/scripts/thread-cert/Cert_6_5_01_ChildResetSynchronize.py
index 01cc5446d..fbf9d8aa2 100755
--- a/tests/scripts/thread-cert/Cert_6_5_01_ChildResetSynchronize.py
+++ b/tests/scripts/thread-cert/Cert_6_5_01_ChildResetSynchronize.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_5_02_ChildResetReattach.py b/tests/scripts/thread-cert/Cert_6_5_02_ChildResetReattach.py
index 2985fc08e..846f6ae6e 100755
--- a/tests/scripts/thread-cert/Cert_6_5_02_ChildResetReattach.py
+++ b/tests/scripts/thread-cert/Cert_6_5_02_ChildResetReattach.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_6_01_KeyIncrement.py b/tests/scripts/thread-cert/Cert_6_6_01_KeyIncrement.py
index 5325b66de..77967a0d9 100755
--- a/tests/scripts/thread-cert/Cert_6_6_01_KeyIncrement.py
+++ b/tests/scripts/thread-cert/Cert_6_6_01_KeyIncrement.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_6_6_02_KeyIncrementRollOver.py b/tests/scripts/thread-cert/Cert_6_6_02_KeyIncrementRollOver.py
index 72ed80a85..766b42b50 100755
--- a/tests/scripts/thread-cert/Cert_6_6_02_KeyIncrementRollOver.py
+++ b/tests/scripts/thread-cert/Cert_6_6_02_KeyIncrementRollOver.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_7_1_01_BorderRouterAsLeader.py b/tests/scripts/thread-cert/Cert_7_1_01_BorderRouterAsLeader.py
index e31b06225..4f02528a7 100755
--- a/tests/scripts/thread-cert/Cert_7_1_01_BorderRouterAsLeader.py
+++ b/tests/scripts/thread-cert/Cert_7_1_01_BorderRouterAsLeader.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_7_1_02_BorderRouterAsRouter.py b/tests/scripts/thread-cert/Cert_7_1_02_BorderRouterAsRouter.py
index da4518bca..22eb0c8ef 100755
--- a/tests/scripts/thread-cert/Cert_7_1_02_BorderRouterAsRouter.py
+++ b/tests/scripts/thread-cert/Cert_7_1_02_BorderRouterAsRouter.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_7_1_03_BorderRouterAsLeader.py b/tests/scripts/thread-cert/Cert_7_1_03_BorderRouterAsLeader.py
index 17333ca30..018cb04ac 100755
--- a/tests/scripts/thread-cert/Cert_7_1_03_BorderRouterAsLeader.py
+++ b/tests/scripts/thread-cert/Cert_7_1_03_BorderRouterAsLeader.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_7_1_04_BorderRouterAsRouter.py b/tests/scripts/thread-cert/Cert_7_1_04_BorderRouterAsRouter.py
index 4d5205b72..7ffb393e7 100755
--- a/tests/scripts/thread-cert/Cert_7_1_04_BorderRouterAsRouter.py
+++ b/tests/scripts/thread-cert/Cert_7_1_04_BorderRouterAsRouter.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_7_1_05_BorderRouterAsRouter.py b/tests/scripts/thread-cert/Cert_7_1_05_BorderRouterAsRouter.py
index fef529939..f048369b5 100755
--- a/tests/scripts/thread-cert/Cert_7_1_05_BorderRouterAsRouter.py
+++ b/tests/scripts/thread-cert/Cert_7_1_05_BorderRouterAsRouter.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_8_1_01_Commissioning.py b/tests/scripts/thread-cert/Cert_8_1_01_Commissioning.py
index 7a9486307..e5ee37434 100755
--- a/tests/scripts/thread-cert/Cert_8_1_01_Commissioning.py
+++ b/tests/scripts/thread-cert/Cert_8_1_01_Commissioning.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_8_1_02_Commissioning.py b/tests/scripts/thread-cert/Cert_8_1_02_Commissioning.py
index 781746595..01c60a204 100755
--- a/tests/scripts/thread-cert/Cert_8_1_02_Commissioning.py
+++ b/tests/scripts/thread-cert/Cert_8_1_02_Commissioning.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_8_2_01_JoinerRouter.py b/tests/scripts/thread-cert/Cert_8_2_01_JoinerRouter.py
index 0b4b6f5a9..0cb54bb65 100755
--- a/tests/scripts/thread-cert/Cert_8_2_01_JoinerRouter.py
+++ b/tests/scripts/thread-cert/Cert_8_2_01_JoinerRouter.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_8_2_02_JoinerRouter.py b/tests/scripts/thread-cert/Cert_8_2_02_JoinerRouter.py
index a3851f3cf..e3e7354c0 100755
--- a/tests/scripts/thread-cert/Cert_8_2_02_JoinerRouter.py
+++ b/tests/scripts/thread-cert/Cert_8_2_02_JoinerRouter.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_02_MGMTCommissionerSet.py b/tests/scripts/thread-cert/Cert_9_2_02_MGMTCommissionerSet.py
index 2d7b19c28..942c39314 100755
--- a/tests/scripts/thread-cert/Cert_9_2_02_MGMTCommissionerSet.py
+++ b/tests/scripts/thread-cert/Cert_9_2_02_MGMTCommissionerSet.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_04_ActiveDataset.py b/tests/scripts/thread-cert/Cert_9_2_04_ActiveDataset.py
index 99245685b..1351e533e 100755
--- a/tests/scripts/thread-cert/Cert_9_2_04_ActiveDataset.py
+++ b/tests/scripts/thread-cert/Cert_9_2_04_ActiveDataset.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_07_DelayTimer.py b/tests/scripts/thread-cert/Cert_9_2_07_DelayTimer.py
index 9a028a58f..585d11316 100755
--- a/tests/scripts/thread-cert/Cert_9_2_07_DelayTimer.py
+++ b/tests/scripts/thread-cert/Cert_9_2_07_DelayTimer.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_08_PersistentDatasets.py b/tests/scripts/thread-cert/Cert_9_2_08_PersistentDatasets.py
index 80591c02a..b6b1b2a66 100755
--- a/tests/scripts/thread-cert/Cert_9_2_08_PersistentDatasets.py
+++ b/tests/scripts/thread-cert/Cert_9_2_08_PersistentDatasets.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_09_PendingPartition.py b/tests/scripts/thread-cert/Cert_9_2_09_PendingPartition.py
index 0b444a42b..53db38a39 100755
--- a/tests/scripts/thread-cert/Cert_9_2_09_PendingPartition.py
+++ b/tests/scripts/thread-cert/Cert_9_2_09_PendingPartition.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_10_PendingPartition.py b/tests/scripts/thread-cert/Cert_9_2_10_PendingPartition.py
index 46868e1f2..42ed0f7ef 100755
--- a/tests/scripts/thread-cert/Cert_9_2_10_PendingPartition.py
+++ b/tests/scripts/thread-cert/Cert_9_2_10_PendingPartition.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_11_MasterKey.py b/tests/scripts/thread-cert/Cert_9_2_11_MasterKey.py
index e09dad29d..1947990e8 100755
--- a/tests/scripts/thread-cert/Cert_9_2_11_MasterKey.py
+++ b/tests/scripts/thread-cert/Cert_9_2_11_MasterKey.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_12_Announce.py b/tests/scripts/thread-cert/Cert_9_2_12_Announce.py
index feb50b6b9..4f6485de7 100755
--- a/tests/scripts/thread-cert/Cert_9_2_12_Announce.py
+++ b/tests/scripts/thread-cert/Cert_9_2_12_Announce.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_13_EnergyScan.py b/tests/scripts/thread-cert/Cert_9_2_13_EnergyScan.py
index d57989015..8fe47a8ef 100755
--- a/tests/scripts/thread-cert/Cert_9_2_13_EnergyScan.py
+++ b/tests/scripts/thread-cert/Cert_9_2_13_EnergyScan.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_14_PanIdQuery.py b/tests/scripts/thread-cert/Cert_9_2_14_PanIdQuery.py
index be2b14646..3cda81422 100755
--- a/tests/scripts/thread-cert/Cert_9_2_14_PanIdQuery.py
+++ b/tests/scripts/thread-cert/Cert_9_2_14_PanIdQuery.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_15_PendingPartition.py b/tests/scripts/thread-cert/Cert_9_2_15_PendingPartition.py
index 7883de373..03c9b9935 100755
--- a/tests/scripts/thread-cert/Cert_9_2_15_PendingPartition.py
+++ b/tests/scripts/thread-cert/Cert_9_2_15_PendingPartition.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_16_ActivePendingPartition.py b/tests/scripts/thread-cert/Cert_9_2_16_ActivePendingPartition.py
index e791cefce..725928a4f 100755
--- a/tests/scripts/thread-cert/Cert_9_2_16_ActivePendingPartition.py
+++ b/tests/scripts/thread-cert/Cert_9_2_16_ActivePendingPartition.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_17_Orphan.py b/tests/scripts/thread-cert/Cert_9_2_17_Orphan.py
index a5cba0789..2e9cbed77 100755
--- a/tests/scripts/thread-cert/Cert_9_2_17_Orphan.py
+++ b/tests/scripts/thread-cert/Cert_9_2_17_Orphan.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Cert_9_2_18_RollBackActiveTimestamp.py b/tests/scripts/thread-cert/Cert_9_2_18_RollBackActiveTimestamp.py
index 7292d2baf..3a8fc7db0 100755
--- a/tests/scripts/thread-cert/Cert_9_2_18_RollBackActiveTimestamp.py
+++ b/tests/scripts/thread-cert/Cert_9_2_18_RollBackActiveTimestamp.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Test_Cli.py b/tests/scripts/thread-cert/Test_Cli.py
index 50d214a38..cfe688e3b 100755
--- a/tests/scripts/thread-cert/Test_Cli.py
+++ b/tests/scripts/thread-cert/Test_Cli.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/Test_MacScan.py b/tests/scripts/thread-cert/Test_MacScan.py
index 0b68c0b54..04ccce37e 100755
--- a/tests/scripts/thread-cert/Test_MacScan.py
+++ b/tests/scripts/thread-cert/Test_MacScan.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/__init__.py b/tests/scripts/thread-cert/__init__.py
index 81888632e..ebde8c027 100755
--- a/tests/scripts/thread-cert/__init__.py
+++ b/tests/scripts/thread-cert/__init__.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/coap.py b/tests/scripts/thread-cert/coap.py
index ea926b59c..68ec87180 100644
--- a/tests/scripts/thread-cert/coap.py
+++ b/tests/scripts/thread-cert/coap.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/command.py b/tests/scripts/thread-cert/command.py
index 043dfe61e..bf32ad5c5 100644
--- a/tests/scripts/thread-cert/command.py
+++ b/tests/scripts/thread-cert/command.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2017-2018, The OpenThread Authors.
 #  All rights reserved.
@@ -28,7 +28,6 @@
 #
 
 import binascii
-import sys
 
 import ipv6
 import network_data
@@ -70,8 +69,6 @@ def check_address_query(command_msg, source_node, destination_address):
 
     if isinstance(destination_address, bytearray):
         destination_address = bytes(destination_address)
-    elif isinstance(destination_address, str) and sys.version_info[0] == 2:
-        destination_address = destination_address.decode("utf-8")
 
     assert (
         ipv6.ip_address(destination_address)
@@ -124,8 +121,6 @@ def check_address_error_notification(
 
     if isinstance(destination_address, bytearray):
         destination_address = bytes(destination_address)
-    elif isinstance(destination_address, str) and sys.version_info[0] == 2:
-        destination_address = destination_address.decode("utf-8")
 
     assert (
         ipv6.ip_address(destination_address)
diff --git a/tests/scripts/thread-cert/common.py b/tests/scripts/thread-cert/common.py
index 4e460af2f..519b1df44 100644
--- a/tests/scripts/thread-cert/common.py
+++ b/tests/scripts/thread-cert/common.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
@@ -28,7 +28,6 @@
 #
 
 import struct
-import sys
 
 from binascii import hexlify
 from enum import IntEnum
@@ -69,9 +68,6 @@ class MessageInfo(object):
         if isinstance(value, bytearray):
             value = bytes(value)
 
-        elif isinstance(value, str) and sys.version_info[0] == 2:
-            value = value.decode("utf-8")
-
         return ipaddress.ip_address(value)
 
     @property
diff --git a/tests/scripts/thread-cert/config.py b/tests/scripts/thread-cert/config.py
index 382410b87..043bc2022 100644
--- a/tests/scripts/thread-cert/config.py
+++ b/tests/scripts/thread-cert/config.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/debug.py b/tests/scripts/thread-cert/debug.py
index d4fd81767..4d76097a9 100644
--- a/tests/scripts/thread-cert/debug.py
+++ b/tests/scripts/thread-cert/debug.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/dtls.py b/tests/scripts/thread-cert/dtls.py
index 8a86b34a6..33fd91461 100644
--- a/tests/scripts/thread-cert/dtls.py
+++ b/tests/scripts/thread-cert/dtls.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/ipv6.py b/tests/scripts/thread-cert/ipv6.py
index 730303ce0..9e285de16 100644
--- a/tests/scripts/thread-cert/ipv6.py
+++ b/tests/scripts/thread-cert/ipv6.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
@@ -30,7 +30,6 @@
 import abc
 import io
 import struct
-import sys
 
 from binascii import hexlify
 from ipaddress import ip_address
@@ -223,9 +222,6 @@ class IPv6PseudoHeader(ConvertibleToBytes):
         if isinstance(value, bytearray):
             value = bytes(value)
 
-        elif isinstance(value, str) and sys.version_info[0] == 2:
-            value = value.decode("utf-8")
-
         return ip_address(value)
 
     @property
@@ -287,9 +283,6 @@ class IPv6Header(ConvertibleToBytes, BuildableFromBytes):
         if isinstance(value, bytearray):
             value = bytes(value)
 
-        elif isinstance(value, str) and sys.version_info[0] == 2:
-            value = value.decode("utf-8")
-
         return ip_address(value)
 
     @property
diff --git a/tests/scripts/thread-cert/lowpan.py b/tests/scripts/thread-cert/lowpan.py
index 43ec9dee5..01fac9055 100644
--- a/tests/scripts/thread-cert/lowpan.py
+++ b/tests/scripts/thread-cert/lowpan.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
@@ -30,7 +30,6 @@
 import io
 import ipaddress
 import struct
-import sys
 
 import common
 import ipv6
@@ -320,9 +319,6 @@ class LowpanUdpHeaderFactory:
 class Context:
     def __init__(self, prefix, prefix_length=None):
         if isinstance(prefix, str):
-            if sys.version_info[0] == 2:
-                prefix = prefix.decode("utf-8")
-
             prefix, prefix_length = prefix.split("/")
             prefix_length = int(prefix_length)
 
diff --git a/tests/scripts/thread-cert/mac802154.py b/tests/scripts/thread-cert/mac802154.py
index 09a677306..7d117603c 100644
--- a/tests/scripts/thread-cert/mac802154.py
+++ b/tests/scripts/thread-cert/mac802154.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/mesh_cop.py b/tests/scripts/thread-cert/mesh_cop.py
index 649813d00..f5abcb10f 100644
--- a/tests/scripts/thread-cert/mesh_cop.py
+++ b/tests/scripts/thread-cert/mesh_cop.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/message.py b/tests/scripts/thread-cert/message.py
index 73761aa60..4894efcff 100644
--- a/tests/scripts/thread-cert/message.py
+++ b/tests/scripts/thread-cert/message.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
@@ -30,7 +30,6 @@
 import io
 import ipaddress
 import struct
-import sys
 
 import coap
 import common
@@ -349,9 +348,6 @@ class Message(object):
         assert sent_to_node
 
     def assertSentToDestinationAddress(self, ipv6_address):
-        if sys.version_info[0] == 2:
-            ipv6_address = ipv6_address.decode("utf-8")
-
         assert (
             self.ipv6_packet.ipv6_header.destination_address
             == ipaddress.ip_address(ipv6_address)
diff --git a/tests/scripts/thread-cert/mle.py b/tests/scripts/thread-cert/mle.py
index 4c3e05dc8..0f6e335a7 100644
--- a/tests/scripts/thread-cert/mle.py
+++ b/tests/scripts/thread-cert/mle.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/net_crypto.py b/tests/scripts/thread-cert/net_crypto.py
index a2f7abaa7..191fa0063 100644
--- a/tests/scripts/thread-cert/net_crypto.py
+++ b/tests/scripts/thread-cert/net_crypto.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/network_data.py b/tests/scripts/thread-cert/network_data.py
index edf40f86f..72c3ce19b 100644
--- a/tests/scripts/thread-cert/network_data.py
+++ b/tests/scripts/thread-cert/network_data.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/network_layer.py b/tests/scripts/thread-cert/network_layer.py
index 99081fb7f..a84c6495b 100644
--- a/tests/scripts/thread-cert/network_layer.py
+++ b/tests/scripts/thread-cert/network_layer.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/node.py b/tests/scripts/thread-cert/node.py
index fffb393b5..7ddcd37ee 100755
--- a/tests/scripts/thread-cert/node.py
+++ b/tests/scripts/thread-cert/node.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
@@ -60,10 +60,7 @@ class Node:
             self.__init_sim(nodeid, mode)
 
         if self.verbose:
-            if sys.version_info[0] == 2:
-                self.pexpect.logfile_read = sys.stdout
-            else:
-                self.pexpect.logfile_read = sys.stdout.buffer
+            self.pexpect.logfile_read = sys.stdout.buffer
 
         self._initialized = True
 
@@ -543,8 +540,6 @@ class Node:
         for addr in addrs:
             if isinstance(addr, bytearray):
                 addr = bytes(addr)
-            elif isinstance(addr, str) and sys.version_info[0] == 2:
-                addr = addr.decode("utf-8")
             ipv6_address = ipaddress.ip_address(addr)
             if ipv6_address in network:
                 return ipv6_address.exploded
diff --git a/tests/scripts/thread-cert/pcap.py b/tests/scripts/thread-cert/pcap.py
index 51e88c80a..8887b493f 100644
--- a/tests/scripts/thread-cert/pcap.py
+++ b/tests/scripts/thread-cert/pcap.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/requirements.txt b/tests/scripts/thread-cert/requirements.txt
index e4c96963f..684b969b6 100644
--- a/tests/scripts/thread-cert/requirements.txt
+++ b/tests/scripts/thread-cert/requirements.txt
@@ -1,5 +1,4 @@
-enum34==1.1.2;python_version<"3.4"
-future==0.16.0
-ipaddress==1.0.16
-pexpect==4.6
-pycryptodome==3.6.6
+enum34
+ipaddress
+pexpect
+pycryptodome
diff --git a/tests/scripts/thread-cert/simulator.py b/tests/scripts/thread-cert/simulator.py
index 7588e1bf6..fb23ec558 100644
--- a/tests/scripts/thread-cert/simulator.py
+++ b/tests/scripts/thread-cert/simulator.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/sniffer.py b/tests/scripts/thread-cert/sniffer.py
index a181b5f34..5bfbb825f 100644
--- a/tests/scripts/thread-cert/sniffer.py
+++ b/tests/scripts/thread-cert/sniffer.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/sniffer_transport.py b/tests/scripts/thread-cert/sniffer_transport.py
index 3e041e66e..6f443d3bb 100644
--- a/tests/scripts/thread-cert/sniffer_transport.py
+++ b/tests/scripts/thread-cert/sniffer_transport.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_coap.py b/tests/scripts/thread-cert/test_coap.py
index 63cb2c6f1..35d4bb6a6 100755
--- a/tests/scripts/thread-cert/test_coap.py
+++ b/tests/scripts/thread-cert/test_coap.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_coaps.py b/tests/scripts/thread-cert/test_coaps.py
index a134087ba..bb4636652 100755
--- a/tests/scripts/thread-cert/test_coaps.py
+++ b/tests/scripts/thread-cert/test_coaps.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_common.py b/tests/scripts/thread-cert/test_common.py
index 8a80b054e..42939cd42 100755
--- a/tests/scripts/thread-cert/test_common.py
+++ b/tests/scripts/thread-cert/test_common.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_crypto.py b/tests/scripts/thread-cert/test_crypto.py
index 633d208a9..3e00407c5 100755
--- a/tests/scripts/thread-cert/test_crypto.py
+++ b/tests/scripts/thread-cert/test_crypto.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_diag.py b/tests/scripts/thread-cert/test_diag.py
index 2303952a2..06a92fdc1 100755
--- a/tests/scripts/thread-cert/test_diag.py
+++ b/tests/scripts/thread-cert/test_diag.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_ipv6.py b/tests/scripts/thread-cert/test_ipv6.py
index c0b72c097..8011e1208 100755
--- a/tests/scripts/thread-cert/test_ipv6.py
+++ b/tests/scripts/thread-cert/test_ipv6.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_ipv6_fragmentation.py b/tests/scripts/thread-cert/test_ipv6_fragmentation.py
index 4cbb09b30..90bb4408a 100755
--- a/tests/scripts/thread-cert/test_ipv6_fragmentation.py
+++ b/tests/scripts/thread-cert/test_ipv6_fragmentation.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_lowpan.py b/tests/scripts/thread-cert/test_lowpan.py
index 5142b79a6..04ebc1c99 100755
--- a/tests/scripts/thread-cert/test_lowpan.py
+++ b/tests/scripts/thread-cert/test_lowpan.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_mac802154.py b/tests/scripts/thread-cert/test_mac802154.py
index 2bd10a827..449c7adff 100755
--- a/tests/scripts/thread-cert/test_mac802154.py
+++ b/tests/scripts/thread-cert/test_mac802154.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_mle.py b/tests/scripts/thread-cert/test_mle.py
index 9c5b0a8d0..01526eedc 100755
--- a/tests/scripts/thread-cert/test_mle.py
+++ b/tests/scripts/thread-cert/test_mle.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_network_data.py b/tests/scripts/thread-cert/test_network_data.py
index e72b9c70f..552cc048a 100755
--- a/tests/scripts/thread-cert/test_network_data.py
+++ b/tests/scripts/thread-cert/test_network_data.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_network_layer.py b/tests/scripts/thread-cert/test_network_layer.py
index f7cbfa327..93cae84f2 100755
--- a/tests/scripts/thread-cert/test_network_layer.py
+++ b/tests/scripts/thread-cert/test_network_layer.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2016, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_route_table.py b/tests/scripts/thread-cert/test_route_table.py
index 11c1be51b..18fecdc68 100755
--- a/tests/scripts/thread-cert/test_route_table.py
+++ b/tests/scripts/thread-cert/test_route_table.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/test_service.py b/tests/scripts/thread-cert/test_service.py
index e5876237f..b4dc97caa 100755
--- a/tests/scripts/thread-cert/test_service.py
+++ b/tests/scripts/thread-cert/test_service.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2017, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/scripts/thread-cert/tlvs_parsing.py b/tests/scripts/thread-cert/tlvs_parsing.py
index 06af83d3c..63195ff81 100644
--- a/tests/scripts/thread-cert/tlvs_parsing.py
+++ b/tests/scripts/thread-cert/tlvs_parsing.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-001-get-set.py b/tests/toranj/test-001-get-set.py
index a5d34338b..c8a841df4 100644
--- a/tests/toranj/test-001-get-set.py
+++ b/tests/toranj/test-001-get-set.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-002-form.py b/tests/toranj/test-002-form.py
index 50db64af8..f74b80997 100644
--- a/tests/toranj/test-002-form.py
+++ b/tests/toranj/test-002-form.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-003-join.py b/tests/toranj/test-003-join.py
index c39dcefad..114cf8184 100644
--- a/tests/toranj/test-003-join.py
+++ b/tests/toranj/test-003-join.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-004-scan.py b/tests/toranj/test-004-scan.py
index 5012b3df3..ff4603ef4 100644
--- a/tests/toranj/test-004-scan.py
+++ b/tests/toranj/test-004-scan.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-005-discover-scan.py b/tests/toranj/test-005-discover-scan.py
index 33400e0d6..e7074e64e 100644
--- a/tests/toranj/test-005-discover-scan.py
+++ b/tests/toranj/test-005-discover-scan.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-006-traffic-router-end-device.py b/tests/toranj/test-006-traffic-router-end-device.py
index c3398d453..314e6a521 100644
--- a/tests/toranj/test-006-traffic-router-end-device.py
+++ b/tests/toranj/test-006-traffic-router-end-device.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-007-traffic-router-sleepy.py b/tests/toranj/test-007-traffic-router-sleepy.py
index b0842b865..241e29143 100644
--- a/tests/toranj/test-007-traffic-router-sleepy.py
+++ b/tests/toranj/test-007-traffic-router-sleepy.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-008-permit-join.py b/tests/toranj/test-008-permit-join.py
index 3a66f74f5..63ded3272 100644
--- a/tests/toranj/test-008-permit-join.py
+++ b/tests/toranj/test-008-permit-join.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-009-insecure-traffic-join.py b/tests/toranj/test-009-insecure-traffic-join.py
index 02c7e260c..d8268c47a 100644
--- a/tests/toranj/test-009-insecure-traffic-join.py
+++ b/tests/toranj/test-009-insecure-traffic-join.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-010-on-mesh-prefix-config-gateway.py b/tests/toranj/test-010-on-mesh-prefix-config-gateway.py
index eae1ac44e..c096b1a55 100644
--- a/tests/toranj/test-010-on-mesh-prefix-config-gateway.py
+++ b/tests/toranj/test-010-on-mesh-prefix-config-gateway.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-011-child-table.py b/tests/toranj/test-011-child-table.py
index 6a155d064..27e8d2432 100644
--- a/tests/toranj/test-011-child-table.py
+++ b/tests/toranj/test-011-child-table.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-012-multi-hop-traffic.py b/tests/toranj/test-012-multi-hop-traffic.py
index eb8c350c3..e825331e6 100644
--- a/tests/toranj/test-012-multi-hop-traffic.py
+++ b/tests/toranj/test-012-multi-hop-traffic.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-013-off-mesh-route-traffic.py b/tests/toranj/test-013-off-mesh-route-traffic.py
index 1f91fbfaa..3009c20e1 100644
--- a/tests/toranj/test-013-off-mesh-route-traffic.py
+++ b/tests/toranj/test-013-off-mesh-route-traffic.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-014-ip6-address-add.py b/tests/toranj/test-014-ip6-address-add.py
index 74cdf4607..c9822d05d 100644
--- a/tests/toranj/test-014-ip6-address-add.py
+++ b/tests/toranj/test-014-ip6-address-add.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-015-same-prefix-on-multiple-nodes.py b/tests/toranj/test-015-same-prefix-on-multiple-nodes.py
index 19c61e288..fcb07a416 100644
--- a/tests/toranj/test-015-same-prefix-on-multiple-nodes.py
+++ b/tests/toranj/test-015-same-prefix-on-multiple-nodes.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-016-neighbor-table.py b/tests/toranj/test-016-neighbor-table.py
index 0fdbca889..c8bac848d 100644
--- a/tests/toranj/test-016-neighbor-table.py
+++ b/tests/toranj/test-016-neighbor-table.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-017-parent-reset-child-recovery.py b/tests/toranj/test-017-parent-reset-child-recovery.py
index 3d66a57bf..b7fec12fd 100644
--- a/tests/toranj/test-017-parent-reset-child-recovery.py
+++ b/tests/toranj/test-017-parent-reset-child-recovery.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-018-child-supervision.py b/tests/toranj/test-018-child-supervision.py
index 29c2a5b59..5c02bb696 100644
--- a/tests/toranj/test-018-child-supervision.py
+++ b/tests/toranj/test-018-child-supervision.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-019-inform-previous-parent.py b/tests/toranj/test-019-inform-previous-parent.py
index c96097ddc..d88451c11 100644
--- a/tests/toranj/test-019-inform-previous-parent.py
+++ b/tests/toranj/test-019-inform-previous-parent.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-020-router-table.py b/tests/toranj/test-020-router-table.py
index 961930c02..0c9ac3cdf 100644
--- a/tests/toranj/test-020-router-table.py
+++ b/tests/toranj/test-020-router-table.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-021-address-cache-table.py b/tests/toranj/test-021-address-cache-table.py
index b2bad6321..84b611d4c 100644
--- a/tests/toranj/test-021-address-cache-table.py
+++ b/tests/toranj/test-021-address-cache-table.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-022-multicast-ip6-address.py b/tests/toranj/test-022-multicast-ip6-address.py
index 428e73183..3db89defa 100644
--- a/tests/toranj/test-022-multicast-ip6-address.py
+++ b/tests/toranj/test-022-multicast-ip6-address.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-023-multicast-traffic.py b/tests/toranj/test-023-multicast-traffic.py
index ec1670411..1467423c5 100644
--- a/tests/toranj/test-023-multicast-traffic.py
+++ b/tests/toranj/test-023-multicast-traffic.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-024-partition-merge.py b/tests/toranj/test-024-partition-merge.py
index 8e205ba6c..55899f0c8 100644
--- a/tests/toranj/test-024-partition-merge.py
+++ b/tests/toranj/test-024-partition-merge.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-025-network-data-timeout.py b/tests/toranj/test-025-network-data-timeout.py
index 602a37456..2cab044d4 100644
--- a/tests/toranj/test-025-network-data-timeout.py
+++ b/tests/toranj/test-025-network-data-timeout.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-026-slaac-address-wpantund.py b/tests/toranj/test-026-slaac-address-wpantund.py
index 95b8cc0bf..ab435a780 100644
--- a/tests/toranj/test-026-slaac-address-wpantund.py
+++ b/tests/toranj/test-026-slaac-address-wpantund.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-027-child-mode-change.py b/tests/toranj/test-027-child-mode-change.py
index dbc0cb61a..447e1f4b8 100644
--- a/tests/toranj/test-027-child-mode-change.py
+++ b/tests/toranj/test-027-child-mode-change.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-028-router-leader-reset-recovery.py b/tests/toranj/test-028-router-leader-reset-recovery.py
index 76af349ab..c07738e08 100644
--- a/tests/toranj/test-028-router-leader-reset-recovery.py
+++ b/tests/toranj/test-028-router-leader-reset-recovery.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-029-data-poll-interval.py b/tests/toranj/test-029-data-poll-interval.py
index d2463e3cf..b4213e3a2 100644
--- a/tests/toranj/test-029-data-poll-interval.py
+++ b/tests/toranj/test-029-data-poll-interval.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-030-slaac-address-ncp.py b/tests/toranj/test-030-slaac-address-ncp.py
index 2abbf7d51..c6edda1cc 100644
--- a/tests/toranj/test-030-slaac-address-ncp.py
+++ b/tests/toranj/test-030-slaac-address-ncp.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-031-meshcop-joiner-commissioner.py b/tests/toranj/test-031-meshcop-joiner-commissioner.py
index 30a471dc6..f06e560fc 100644
--- a/tests/toranj/test-031-meshcop-joiner-commissioner.py
+++ b/tests/toranj/test-031-meshcop-joiner-commissioner.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-032-child-attach-with-multiple-ip-addresses.py b/tests/toranj/test-032-child-attach-with-multiple-ip-addresses.py
index 5f986b56c..3992b98a9 100644
--- a/tests/toranj/test-032-child-attach-with-multiple-ip-addresses.py
+++ b/tests/toranj/test-032-child-attach-with-multiple-ip-addresses.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-033-mesh-local-prefix-change.py b/tests/toranj/test-033-mesh-local-prefix-change.py
index bf1126f06..cbf7f7642 100644
--- a/tests/toranj/test-033-mesh-local-prefix-change.py
+++ b/tests/toranj/test-033-mesh-local-prefix-change.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-034-poor-link-parent-child-attach.py b/tests/toranj/test-034-poor-link-parent-child-attach.py
index a10f9ca90..2bcf93c2f 100644
--- a/tests/toranj/test-034-poor-link-parent-child-attach.py
+++ b/tests/toranj/test-034-poor-link-parent-child-attach.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-035-child-timeout-large-data-poll.py b/tests/toranj/test-035-child-timeout-large-data-poll.py
index d9123aadd..6753a94a8 100644
--- a/tests/toranj/test-035-child-timeout-large-data-poll.py
+++ b/tests/toranj/test-035-child-timeout-large-data-poll.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2019, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-100-mcu-power-state.py b/tests/toranj/test-100-mcu-power-state.py
index ec232ec1e..db5aa620b 100644
--- a/tests/toranj/test-100-mcu-power-state.py
+++ b/tests/toranj/test-100-mcu-power-state.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-600-channel-manager-properties.py b/tests/toranj/test-600-channel-manager-properties.py
index 2016fdd76..8e9f72d4d 100644
--- a/tests/toranj/test-600-channel-manager-properties.py
+++ b/tests/toranj/test-600-channel-manager-properties.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-601-channel-manager-channel-change.py b/tests/toranj/test-601-channel-manager-channel-change.py
index d7a363229..561aa30a5 100644
--- a/tests/toranj/test-601-channel-manager-channel-change.py
+++ b/tests/toranj/test-601-channel-manager-channel-change.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-602-channel-manager-channel-select.py b/tests/toranj/test-602-channel-manager-channel-select.py
index d0996b492..253ce03d7 100644
--- a/tests/toranj/test-602-channel-manager-channel-select.py
+++ b/tests/toranj/test-602-channel-manager-channel-select.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-603-channel-manager-announce-recovery.py b/tests/toranj/test-603-channel-manager-announce-recovery.py
index 3712b2e0f..381f68fba 100644
--- a/tests/toranj/test-603-channel-manager-announce-recovery.py
+++ b/tests/toranj/test-603-channel-manager-announce-recovery.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/test-nnn-template.py b/tests/toranj/test-nnn-template.py
index 0a4e6b427..d8ec956d6 100644
--- a/tests/toranj/test-nnn-template.py
+++ b/tests/toranj/test-nnn-template.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.
diff --git a/tests/toranj/wpan.py b/tests/toranj/wpan.py
index f0dd3fac2..84158de12 100644
--- a/tests/toranj/wpan.py
+++ b/tests/toranj/wpan.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 #  Copyright (c) 2018, The OpenThread Authors.
 #  All rights reserved.