diff --git a/changelog.d/18070.feature b/changelog.d/18070.feature
new file mode 100644
index 0000000000..1bfa0f9246
--- /dev/null
+++ b/changelog.d/18070.feature
@@ -0,0 +1 @@
+Add `via` param to hierarchy endpoint. Contributed by Krishan (@kfiven).
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index 0a963b121a..3dc3abeebe 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -560,3 +560,6 @@ class ExperimentalConfig(Config):
 
         # MSC4076: Add `disable_badge_count`` to pusher configuration
         self.msc4076_enabled: bool = experimental.get("msc4076_enabled", False)
+
+        # MSC4235: Add `via` param to hierarchy endpoint
+        self.msc4235_enabled: bool = experimental.get("msc4235_enabled", False)
diff --git a/synapse/handlers/room_summary.py b/synapse/handlers/room_summary.py
index 64f5bea014..57161fb02c 100644
--- a/synapse/handlers/room_summary.py
+++ b/synapse/handlers/room_summary.py
@@ -111,7 +111,15 @@ class RoomSummaryHandler:
         # If a user tries to fetch the same page multiple times in quick succession,
         # only process the first attempt and return its result to subsequent requests.
         self._pagination_response_cache: ResponseCache[
-            Tuple[str, str, bool, Optional[int], Optional[int], Optional[str]]
+            Tuple[
+                str,
+                str,
+                bool,
+                Optional[int],
+                Optional[int],
+                Optional[str],
+                Optional[List[str]],
+            ]
         ] = ResponseCache(
             hs.get_clock(),
             "get_room_hierarchy",
@@ -126,6 +134,7 @@ class RoomSummaryHandler:
         max_depth: Optional[int] = None,
         limit: Optional[int] = None,
         from_token: Optional[str] = None,
+        remote_room_hosts: Optional[List[str]] = None,
     ) -> JsonDict:
         """
         Implementation of the room hierarchy C-S API.
@@ -162,6 +171,7 @@ class RoomSummaryHandler:
                 max_depth,
                 limit,
                 from_token,
+                remote_room_hosts,
             ),
             self._get_room_hierarchy,
             requester.user.to_string(),
@@ -170,6 +180,7 @@ class RoomSummaryHandler:
             max_depth,
             limit,
             from_token,
+            remote_room_hosts,
         )
 
     async def _get_room_hierarchy(
@@ -180,6 +191,7 @@ class RoomSummaryHandler:
         max_depth: Optional[int] = None,
         limit: Optional[int] = None,
         from_token: Optional[str] = None,
+        remote_room_hosts: Optional[List[str]] = None,
     ) -> JsonDict:
         """See docstring for SpaceSummaryHandler.get_room_hierarchy."""
 
@@ -199,7 +211,7 @@ class RoomSummaryHandler:
 
         if not local_room:
             room_hierarchy = await self._summarize_remote_room_hierarchy(
-                _RoomQueueEntry(requested_room_id, ()),
+                _RoomQueueEntry(requested_room_id, remote_room_hosts or ()),
                 False,
             )
             root_room_entry = room_hierarchy[0]
@@ -240,7 +252,7 @@ class RoomSummaryHandler:
             processed_rooms = set(pagination_session["processed_rooms"])
         else:
             # The queue of rooms to process, the next room is last on the stack.
-            room_queue = [_RoomQueueEntry(requested_room_id, ())]
+            room_queue = [_RoomQueueEntry(requested_room_id, remote_room_hosts or ())]
 
             # Rooms we have already processed.
             processed_rooms = set()
diff --git a/synapse/rest/client/room.py b/synapse/rest/client/room.py
index 03e7bc0a24..5b6ec9b17d 100644
--- a/synapse/rest/client/room.py
+++ b/synapse/rest/client/room.py
@@ -1517,6 +1517,7 @@ class RoomHierarchyRestServlet(RestServlet):
         super().__init__()
         self._auth = hs.get_auth()
         self._room_summary_handler = hs.get_room_summary_handler()
+        self.msc4235_enabled = hs.config.experimental.msc4235_enabled
 
     async def on_GET(
         self, request: SynapseRequest, room_id: str
@@ -1526,6 +1527,14 @@ class RoomHierarchyRestServlet(RestServlet):
         max_depth = parse_integer(request, "max_depth")
         limit = parse_integer(request, "limit")
 
+        # twisted.web.server.Request.args is incorrectly defined as Optional[Any]
+        remote_room_hosts = None
+        if self.msc4235_enabled:
+            args: Dict[bytes, List[bytes]] = request.args  # type: ignore
+            remote_room_hosts = parse_strings_from_args(
+                args, "org.matrix.msc4235.via", required=False
+            )
+
         return 200, await self._room_summary_handler.get_room_hierarchy(
             requester,
             room_id,
@@ -1533,6 +1542,7 @@ class RoomHierarchyRestServlet(RestServlet):
             max_depth=max_depth,
             limit=limit,
             from_token=parse_string(request, "from"),
+            remote_room_hosts=remote_room_hosts,
         )