diff --git a/changelogs/fragments/synchronize_remote_is_local.yaml b/changelogs/fragments/synchronize_remote_is_local.yaml
new file mode 100644
index 0000000000..fd5d8e2acf
--- /dev/null
+++ b/changelogs/fragments/synchronize_remote_is_local.yaml
@@ -0,0 +1,2 @@
+bugfixes:
+- synchronize - Ensure the local connection created by synchronize uses _remote_is_local=True, which causes ActionBase to build a local tmpdir (https://github.com/ansible/ansible/pull/40833)
diff --git a/lib/ansible/plugins/action/synchronize.py b/lib/ansible/plugins/action/synchronize.py
index 54b053cb0e..2bb5b7c786 100644
--- a/lib/ansible/plugins/action/synchronize.py
+++ b/lib/ansible/plugins/action/synchronize.py
@@ -301,6 +301,9 @@ class ActionModule(ActionBase):
 
             new_connection = connection_loader.get('local', self._play_context, new_stdin)
             self._connection = new_connection
+            # Override _remote_is_local as an instance attribute specifically for the synchronize use case
+            # ensuring we set local tmpdir correctly
+            self._connection._remote_is_local = True
             self._override_module_replaced_vars(task_vars)
 
         # SWITCH SRC AND DEST HOST PER MODE
diff --git a/test/units/plugins/action/test_synchronize.py b/test/units/plugins/action/test_synchronize.py
index 5d5ea26a13..23e64e9149 100644
--- a/test/units/plugins/action/test_synchronize.py
+++ b/test/units/plugins/action/test_synchronize.py
@@ -42,6 +42,10 @@ with open('task_vars.json', 'wb') as f:
 '''
 
 
+class BreakPoint(Exception):
+    pass
+
+
 class TaskMock(object):
     args = {'src': u'/tmp/deleteme',
             'dest': '/tmp/deleteme',
@@ -246,3 +250,15 @@ class TestSynchronizeAction(unittest.TestCase):
         # delegate to other remote host with su enabled
         x = SynchronizeTester()
         x.runtest(fixturepath=os.path.join(self.fixturedir, 'delegate_remote_su'))
+
+    @patch.object(ActionModule, '_low_level_execute_command', side_effect=BreakPoint)
+    @patch.object(ActionModule, '_remote_expand_user', side_effect=ActionModule._remote_expand_user, autospec=True)
+    def test_remote_user_not_in_local_tmpdir(self, spy_remote_expand_user, ll_ec):
+        x = SynchronizeTester()
+        SAM = ActionModule(x.task, x.connection, x._play_context,
+                           x.loader, x.templar, x.shared_loader_obj)
+        try:
+            SAM.run(task_vars={'hostvars': {'foo': {}, 'localhost': {}}, 'inventory_hostname': 'foo'})
+        except BreakPoint:
+            pass
+        self.assertEqual(spy_remote_expand_user.call_count, 0)