diff --git a/CMakeLists.txt b/CMakeLists.txt
index f85615f..1fa4c99 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -17,6 +17,8 @@
     "${mbed-os_SOURCE_DIR}/platform/FEATURE_EXPERIMENTAL_API/FEATURE_PSA/TARGET_TFM/TARGET_TFM_LATEST/scripts;${mbed-os_SOURCE_DIR}/targets/TARGET_Cypress/scripts;${mbed-os_SOURCE_DIR}/targets/TARGET_NXP/scripts"
 )
 
+add_subdirectory(extern)
+
 option(BUILD_TESTING "Run unit tests only." OFF)
 
 if(CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME AND BUILD_TESTING)
diff --git a/extern/CMakeLists.txt b/extern/CMakeLists.txt
new file mode 100644
index 0000000..8441653
--- /dev/null
+++ b/extern/CMakeLists.txt
@@ -0,0 +1,12 @@
+# Copyright (c) 2021 ARM Limited. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+include(FetchContent)
+
+FetchContent_Declare(
+    greentea-client
+    GIT_REPOSITORY  https://github.com/ARMmbed/greentea-client.git
+    GIT_TAG         472aad2327fbfde827852fc44775904706847a3a
+)
+
+FetchContent_MakeAvailable(greentea-client)