diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-10-21-21-26-10.gh-issue-159739.Aw61LR.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-10-21-21-26-10.gh-issue-159739.Aw61LR.rst
new file mode 100644
index 00000000000000..5de64814b1ca55
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-10-21-21-26-10.gh-issue-159739.Aw61LR.rst
@@ -0,0 +1 @@
+Fix a race in ``list.__sizeof__()`` when a list is concurrently resized on a free-threaded build.
diff --git a/Objects/listobject.c b/Objects/listobject.c
index b6ebb2b53fc304..c09d4618551e12 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -3602,10 +3602,12 @@ list___sizeof___impl(PyListObject *self)
 {
     size_t res = _PyObject_SIZE(Py_TYPE(self));
 #ifdef Py_GIL_DISABLED
-    PyObject **ob_item = _Py_atomic_load_ptr(&self->ob_item);
+    Py_BEGIN_CRITICAL_SECTION(self);
+    PyObject **ob_item = self->ob_item;
     if (ob_item != NULL) {
         res += list_capacity(ob_item) * sizeof(PyObject *);
     }
+    Py_END_CRITICAL_SECTION();
 #else
     res += (size_t)self->allocated * sizeof(PyObject *);
 #endif