diff --git a/src/posix/platform/platform-posix.h b/src/posix/platform/platform-posix.h
index fbebdb6fa..78dcab40e 100644
--- a/src/posix/platform/platform-posix.h
+++ b/src/posix/platform/platform-posix.h
@@ -97,12 +97,6 @@ struct RadioProcessContext
     const fd_set *mWriteFdSet;
 };
 
-/**
- * Unique node ID.
- *
- */
-extern uint64_t gNodeId;
-
 /**
  * This function initializes the alarm service used by OpenThread.
  *
diff --git a/src/posix/platform/system.cpp b/src/posix/platform/system.cpp
index cd440d8c2..04925f3a5 100644
--- a/src/posix/platform/system.cpp
+++ b/src/posix/platform/system.cpp
@@ -46,8 +46,6 @@
 
 #include "common/code_utils.hpp"
 
-uint64_t gNodeId = 0;
-
 otInstance *otSysInit(otPlatformConfig *aPlatformConfig)
 {
     otInstance *        instance = nullptr;