diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-08-06-11-56-15.gh-issue-137472.Pr_BLB.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-08-06-11-56-15.gh-issue-137472.Pr_BLB.rst
new file mode 100644
index 00000000000000..acfc4dbdea12de
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-08-06-11-56-15.gh-issue-137472.Pr_BLB.rst
@@ -0,0 +1,3 @@
+Fix a crash that can occur in free-threading builds when
+``sys._setprofileallthreads`` or ``sys._settraceallthreads`` changes the
+profile function underneath a running thread.
diff --git a/Python/legacy_tracing.c b/Python/legacy_tracing.c
index dbd19d7755c237..0a0d231cb12d0c 100644
--- a/Python/legacy_tracing.c
+++ b/Python/legacy_tracing.c
@@ -484,13 +484,19 @@ setup_profile(PyThreadState *tstate, Py_tracefunc func, PyObject *arg, PyObject
         }
     }
 
+    _PyEval_StopTheWorld(tstate->interp);
+
     int delta = (func != NULL) - (tstate->c_profilefunc != NULL);
     tstate->c_profilefunc = func;
     *old_profileobj = tstate->c_profileobj;
     tstate->c_profileobj = Py_XNewRef(arg);
     tstate->interp->sys_profiling_threads += delta;
     assert(tstate->interp->sys_profiling_threads >= 0);
-    return tstate->interp->sys_profiling_threads;
+    Py_ssize_t ret = tstate->interp->sys_profiling_threads;
+
+    _PyEval_StartTheWorld(tstate->interp);
+
+    return ret;
 }
 
 int