diff --git a/src/core/diags/factory_diags.cpp b/src/core/diags/factory_diags.cpp
index 12bfefb0e..783b845f8 100644
--- a/src/core/diags/factory_diags.cpp
+++ b/src/core/diags/factory_diags.cpp
@@ -288,6 +288,8 @@ otError Diags::ProcessStart(uint8_t aArgsLength, char *aArgs[], char *aOutput, s
 
     otError error = OT_ERROR_NONE;
 
+    VerifyOrExit(!Get<ThreadNetif>().IsUp(), error = OT_ERROR_INVALID_STATE);
+
     otPlatDiagChannelSet(mChannel);
     otPlatDiagTxPowerSet(mTxPower);
 
diff --git a/tests/scripts/expect/cli-misc.exp b/tests/scripts/expect/cli-misc.exp
index 999efd1e5..65992bb19 100755
--- a/tests/scripts/expect/cli-misc.exp
+++ b/tests/scripts/expect/cli-misc.exp
@@ -164,4 +164,7 @@ expect "0:0:0:0::/64 s low"
 send "route remove ::/64\n"
 expect "Done"
 
+send "diag start\n"
+expect ": InvalidState"
+
 dispose_all