diff --git a/examples/Makefile-nrf52840 b/examples/Makefile-nrf52840
index 3fc029d9b..e78736956 100644
--- a/examples/Makefile-nrf52840
+++ b/examples/Makefile-nrf52840
@@ -124,6 +124,15 @@ ifeq ($(DISABLE_CC310), 1)
 NRF52840_MBEDTLS_CPPFLAGS += -DDISABLE_CC310=1
 endif
 
+ifeq ($(MBEDTLS_THREADING), 1)
+NRF52840_MBEDTLS_CPPFLAGS += -DDISABLE_CC310=1
+NRF52840_MBEDTLS_CPPFLAGS += -DMBEDTLS_THREADING=1
+endif
+
+ifdef MBEDTLS_THREADING_MUTEX_DEF
+NRF52840_MBEDTLS_CPPFLAGS += -DMBEDTLS_THREADING_MUTEX_DEF='\"$(MBEDTLS_THREADING_MUTEX_DEF)\"'
+endif
+
 ifeq ($(shell expr $(GCCVersion) \>= 7), 1)
     COMMONCFLAGS += -Wno-expansion-to-defined
 endif
diff --git a/examples/platforms/nrf52840/README.md b/examples/platforms/nrf52840/README.md
index 69f048955..c166a8953 100644
--- a/examples/platforms/nrf52840/README.md
+++ b/examples/platforms/nrf52840/README.md
@@ -121,6 +121,31 @@ By default, mbedTLS library is built with support for CryptoCell 310 hardware ac
 $ make -f examples/Makefile-nrf52840 DISABLE_CC310=1
 ```
 
+### Optional mbedTLS threading support
+By default, mbedTLS library is built without support for multiple threads. You can enable this built-in support by building OpenThread with the following parameter:
+
+```
+$ make -f examples/Makefile-nrf52840 MBEDTLS_THREADING=1
+```
+
+The simple mutex definition is used as shown below:
+
+```
+typedef void * mbedtls_threading_mutex_t;
+```
+
+However, you can modify it, by providing a path to a header file with proper definition. To do that, build OpenThread with the following parameter:
+
+```
+$ make -f examples/Makefile-nrf52840 MBEDTLS_THREADING=1 MBEDTLS_THREADING_MUTEX_DEF="path_to_a_header_file_with_mutex_definition.h"
+```
+
+See [mbedTls Thread Safety and Multi Threading][mbedtls-thread-safety-and-multi-threading] for more details.
+
+Note that as a temporary limitation CryptoCell 310 hardware acceleration is disabled when using mbedTLS threading.
+
+[mbedtls-thread-safety-and-multi-threading]: https://tls.mbed.org/kb/development/thread-safety-and-multi-threading
+
 ### IEEE EUI-64 address
 
 When the Thread device is configured to obtain the Thread Network security credentials with either Thread Commissioning or an out-of-band method, the extended MAC address should be constructed out of the globally unique IEEE EUI-64.
diff --git a/third_party/NordicSemiconductor/libraries/crypto/nrf52840-mbedtls-config.h b/third_party/NordicSemiconductor/libraries/crypto/nrf52840-mbedtls-config.h
index 6ae51322c..490badb1a 100644
--- a/third_party/NordicSemiconductor/libraries/crypto/nrf52840-mbedtls-config.h
+++ b/third_party/NordicSemiconductor/libraries/crypto/nrf52840-mbedtls-config.h
@@ -32,6 +32,11 @@
 #define MBEDTLS_SHA256_ALT
 #endif // DISABLE_CC310
 
+#ifdef MBEDTLS_THREADING
+#define MBEDTLS_THREADING_C
+#define MBEDTLS_THREADING_ALT
+#endif // MBEDTLS_THREADING
+
 #if defined(__ICCARM__)
     _Pragma("diag_suppress=Pe550")
 #endif
diff --git a/third_party/NordicSemiconductor/libraries/crypto/threading_alt.h b/third_party/NordicSemiconductor/libraries/crypto/threading_alt.h
new file mode 100644
index 000000000..def50ba4a
--- /dev/null
+++ b/third_party/NordicSemiconductor/libraries/crypto/threading_alt.h
@@ -0,0 +1,38 @@
+/*
+ *  Copyright (c) 2019, The OpenThread Authors.
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions are met:
+ *  1. Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *  3. Neither the name of the copyright holder nor the
+ *     names of its contributors may be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *  POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef THREADING_ALT_H_
+#define THREADING_ALT_H_
+
+#ifdef MBEDTLS_THREADING_MUTEX_DEF
+#include MBEDTLS_THREADING_MUTEX_DEF
+#else
+typedef void * mbedtls_threading_mutex_t;
+#endif // MBEDTLS_THREADING_MUTEX_DEF
+
+#endif // THREADING_ALT_H_
diff --git a/third_party/mbedtls/Makefile.am b/third_party/mbedtls/Makefile.am
index 4b4158749..bd923c303 100644
--- a/third_party/mbedtls/Makefile.am
+++ b/third_party/mbedtls/Makefile.am
@@ -75,6 +75,7 @@ libmbedcrypto_a_SOURCES                       = \
     repo/library/ssl_srv.c                      \
     repo/library/ssl_ticket.c                   \
     repo/library/ssl_tls.c                      \
+    repo/library/threading.c                    \
     repo/library/x509.c                         \
     repo/library/x509_crt.c                     \
     $(NULL)