diff --git a/CMakeLists.txt b/CMakeLists.txt
index 00ffb1409..e81b3fb75 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -59,6 +59,14 @@ if(NOT OT_PLATFORM IN_LIST OT_EXAMPLE_PLATFORMS)
     endif()
 endif()
 
+# OT_CONFIG allows users to specify the path to OpenThread project core
+# config header file. The default value of this parameter is empty string.
+# When not specified by user (value is ""), a platform cmake file may
+# choose to change this variable to provide its own core config header
+# file instead.
+
+set(OT_CONFIG "" CACHE STRING "OpenThread project-specific config header file chosen by user at configure time")
+
 list(APPEND OT_PUBLIC_INCLUDES ${PROJECT_BINARY_DIR}/etc/cmake)
 list(APPEND OT_PUBLIC_INCLUDES ${PROJECT_SOURCE_DIR}/etc/cmake)
 list(APPEND OT_PUBLIC_INCLUDES ${PROJECT_SOURCE_DIR}/include)
@@ -71,6 +79,11 @@ elseif(NOT OT_PLATFORM MATCHES "none")
     add_subdirectory("${PROJECT_SOURCE_DIR}/examples/platforms/${OT_PLATFORM}")
 endif()
 
+if(OT_CONFIG)
+    list(APPEND OT_PRIVATE_DEFINES "OPENTHREAD_PROJECT_CORE_CONFIG_FILE=\"${OT_CONFIG}\"")
+    message(STATUS "Project core config: \"${OT_CONFIG}\"")
+endif()
+
 list(APPEND OT_PRIVATE_DEFINES ${OT_PLATFORM_DEFINES})
 
 if(OT_BUILTIN_MBEDTLS)
diff --git a/examples/platforms/cc2538/CMakeLists.txt b/examples/platforms/cc2538/CMakeLists.txt
index f74b6b10c..13ecedb0d 100644
--- a/examples/platforms/cc2538/CMakeLists.txt
+++ b/examples/platforms/cc2538/CMakeLists.txt
@@ -28,13 +28,19 @@
 
 set(OT_PLATFORM_LIB "openthread-cc2538" PARENT_SCOPE)
 
+if(NOT OT_CONFIG)
+    set(OT_CONFIG "openthread-core-cc2538-config.h")
+    set(OT_CONFIG ${OT_CONFIG} PARENT_SCOPE)
+endif()
+
 list(APPEND OT_PLATFORM_DEFINES
-    "OPENTHREAD_PROJECT_CORE_CONFIG_FILE=\"openthread-core-cc2538-config.h\""
     "OPENTHREAD_CORE_CONFIG_PLATFORM_CHECK_FILE=\"openthread-core-cc2538-config-check.h\""
     "OPENTHREAD_CONFIG_NCP_UART_ENABLE=1"
 )
 set(OT_PLATFORM_DEFINES ${OT_PLATFORM_DEFINES} PARENT_SCOPE)
 
+list(APPEND OT_PLATFORM_DEFINES "OPENTHREAD_PROJECT_CORE_CONFIG_FILE=\"${OT_CONFIG}\"")
+
 add_library(openthread-cc2538
     alarm.c
     diag.c
diff --git a/examples/platforms/posix/CMakeLists.txt b/examples/platforms/posix/CMakeLists.txt
index 1de46f514..b4d7229e6 100644
--- a/examples/platforms/posix/CMakeLists.txt
+++ b/examples/platforms/posix/CMakeLists.txt
@@ -28,14 +28,20 @@
 
 set(OT_PLATFORM_LIB "openthread-posix" PARENT_SCOPE)
 
+if(NOT OT_CONFIG)
+    set(OT_CONFIG "openthread-core-posix-config.h")
+    set(OT_CONFIG ${OT_CONFIG} PARENT_SCOPE)
+endif()
+
 list(APPEND OT_PLATFORM_DEFINES
-    "OPENTHREAD_PROJECT_CORE_CONFIG_FILE=\"openthread-core-posix-config.h\""
     "OPENTHREAD_EXAMPLES_POSIX=1"
     "OPENTHREAD_POSIX=1"
     "OPENTHREAD_CONFIG_NCP_UART_ENABLE=1"
 )
 set(OT_PLATFORM_DEFINES ${OT_PLATFORM_DEFINES} PARENT_SCOPE)
 
+list(APPEND OT_PLATFORM_DEFINES "OPENTHREAD_PROJECT_CORE_CONFIG_FILE=\"${OT_CONFIG}\"")
+
 add_library(openthread-posix
     alarm.c
     diag.c