diff --git a/changelog.d/13441.feature b/changelog.d/13441.feature
new file mode 100644
index 0000000000..3a4ae8bf01
--- /dev/null
+++ b/changelog.d/13441.feature
@@ -0,0 +1 @@
+Add remote join capability to the module API's `update_room_membership` method (in a backwards compatible manner).
diff --git a/synapse/module_api/__init__.py b/synapse/module_api/__init__.py
index 71145870ee..87ba154cb7 100644
--- a/synapse/module_api/__init__.py
+++ b/synapse/module_api/__init__.py
@@ -929,10 +929,12 @@ class ModuleApi:
         room_id: str,
         new_membership: str,
         content: Optional[JsonDict] = None,
+        remote_room_hosts: Optional[List[str]] = None,
     ) -> EventBase:
         """Updates the membership of a user to the given value.
 
         Added in Synapse v1.46.0.
+        Changed in Synapse v1.65.0: Added the 'remote_room_hosts' parameter.
 
         Args:
             sender: The user performing the membership change. Must be a user local to
@@ -946,6 +948,7 @@ class ModuleApi:
                 https://spec.matrix.org/unstable/client-server-api/#mroommember for the
                 list of allowed values.
             content: Additional values to include in the resulting event's content.
+            remote_room_hosts: Remote servers to use for remote joins/knocks/etc.
 
         Returns:
             The newly created membership event.
@@ -1005,15 +1008,12 @@ class ModuleApi:
             room_id=room_id,
             action=new_membership,
             content=content,
+            remote_room_hosts=remote_room_hosts,
         )
 
         # Try to retrieve the resulting event.
         event = await self._hs.get_datastores().main.get_event(event_id)
 
-        # update_membership is supposed to always return after the event has been
-        # successfully persisted.
-        assert event is not None
-
         return event
 
     async def create_and_send_event_into_room(self, event_dict: JsonDict) -> EventBase:
diff --git a/tests/module_api/test_api.py b/tests/module_api/test_api.py
index 9bf95472e1..106159fa65 100644
--- a/tests/module_api/test_api.py
+++ b/tests/module_api/test_api.py
@@ -16,6 +16,7 @@ from unittest.mock import Mock
 from twisted.internet import defer
 
 from synapse.api.constants import EduTypes, EventTypes
+from synapse.api.errors import NotFoundError
 from synapse.events import EventBase
 from synapse.federation.units import Transaction
 from synapse.handlers.presence import UserPresenceState
@@ -532,6 +533,34 @@ class ModuleApiTestCase(HomeserverTestCase):
         self.assertEqual(res["displayname"], "simone")
         self.assertIsNone(res["avatar_url"])
 
+    def test_update_room_membership_remote_join(self):
+        """Test that the module API can join a remote room."""
+        # Necessary to fake a remote join.
+        fake_stream_id = 1
+        mocked_remote_join = simple_async_mock(
+            return_value=("fake-event-id", fake_stream_id)
+        )
+        self.hs.get_room_member_handler()._remote_join = mocked_remote_join
+        fake_remote_host = f"{self.module_api.server_name}-remote"
+
+        # Given that the join is to be faked, we expect the relevant join event not to
+        # be persisted and the module API method to raise that.
+        self.get_failure(
+            defer.ensureDeferred(
+                self.module_api.update_room_membership(
+                    sender=f"@user:{self.module_api.server_name}",
+                    target=f"@user:{self.module_api.server_name}",
+                    room_id=f"!nonexistent:{fake_remote_host}",
+                    new_membership="join",
+                    remote_room_hosts=[fake_remote_host],
+                )
+            ),
+            NotFoundError,
+        )
+
+        # Check that a remote join was attempted.
+        self.assertEqual(mocked_remote_join.call_count, 1)
+
     def test_get_room_state(self):
         """Tests that a module can retrieve the state of a room through the module API."""
         user_id = self.register_user("peter", "hackme")