diff --git a/arch/arm/core/aarch32/thread.c b/arch/arm/core/aarch32/thread.c
index 7847171996f..746ec23c691 100644
--- a/arch/arm/core/aarch32/thread.c
+++ b/arch/arm/core/aarch32/thread.c
@@ -509,6 +509,19 @@ void arch_switch_to_main_thread(struct k_thread *main_thread, char *stack_ptr,
 	z_arm_prepare_switch_to_main();
 
 	_current = main_thread;
+
+#if defined(CONFIG_THREAD_LOCAL_STORAGE) && defined(CONFIG_CPU_CORTEX_M)
+	/* On Cortex-M, TLS uses a global variable as pointer to
+	 * the thread local storage area. So this needs to point
+	 * to the main thread's TLS area before switching to any
+	 * thread for the first time, as the pointer is only set
+	 * during context switching.
+	 */
+	extern uintptr_t z_arm_tls_ptr;
+
+	z_arm_tls_ptr = main_thread->tls;
+#endif
+
 #ifdef CONFIG_INSTRUMENT_THREAD_SWITCHING
 	z_thread_mark_switched_in();
 #endif