diff --git a/synapse/app/generic_worker.py b/synapse/app/generic_worker.py
index fa23d9bb20e5..44284727070b 100644
--- a/synapse/app/generic_worker.py
+++ b/synapse/app/generic_worker.py
@@ -108,6 +108,7 @@
 )
 from synapse.rest.client.v2_alpha.keys import KeyChangesServlet, KeyQueryServlet
 from synapse.rest.client.v2_alpha.register import RegisterRestServlet
+from synapse.rest.client.v2_alpha.sendtodevice import SendToDeviceRestServlet
 from synapse.rest.client.versions import VersionsRestServlet
 from synapse.rest.health import HealthResource
 from synapse.rest.key.v2 import KeyApiV2Resource
@@ -520,6 +521,8 @@ def _listen_http(self, listener_config: ListenerConfig):
                     room.register_deprecated_servlets(self, resource)
                     InitialSyncRestServlet(self).register(resource)
 
+                    SendToDeviceRestServlet(self).register(resource)
+
                     user_directory.register_servlets(self, resource)
 
                     # If presence is disabled, use the stub servlet that does
diff --git a/synapse/handlers/devicemessage.py b/synapse/handlers/devicemessage.py
index 276c0f3fc975..5e4ac7fd3331 100644
--- a/synapse/handlers/devicemessage.py
+++ b/synapse/handlers/devicemessage.py
@@ -45,11 +45,23 @@ def __init__(self, hs: "HomeServer"):
         self.store = hs.get_datastore()
         self.notifier = hs.get_notifier()
         self.is_mine = hs.is_mine
-        self.federation = hs.get_federation_sender()
 
-        hs.get_federation_registry().register_edu_handler(
-            "m.direct_to_device", self.on_direct_to_device_edu
-        )
+        # We only need to poke the federation sender explicitly if its on the
+        # same instance.
+        self.federation_sender = None
+        if hs.should_send_federation():
+            self.federation_sender = hs.get_federation_sender()
+
+        # If we can handle the to device EDUs we do so, otherwise we route them
+        # to the appropriate worker.
+        if hs.get_instance_name() in hs.config.worker.writers.to_device:
+            hs.get_federation_registry().register_edu_handler(
+                "m.direct_to_device", self.on_direct_to_device_edu
+            )
+        else:
+            hs.get_federation_registry().register_instances_for_edu(
+                "m.direct_to_device", hs.config.worker.writers.to_device,
+            )
 
         if hs.config.worker.worker_app is None:
             self._user_device_resync = (
@@ -201,7 +213,8 @@ async def send_device_message(
         )
 
         log_kv({"remote_messages": remote_messages})
-        for destination in remote_messages.keys():
-            # Enqueue a new federation transaction to send the new
-            # device messages to each remote destination.
-            self.federation.send_device_messages(destination)
+        if self.federation_sender:
+            for destination in remote_messages.keys():
+                # Enqueue a new federation transaction to send the new
+                # device messages to each remote destination.
+                self.federation_sender.send_device_messages(destination)
diff --git a/synapse/replication/tcp/handler.py b/synapse/replication/tcp/handler.py
index 95e5502bf2b2..1f89249475e7 100644
--- a/synapse/replication/tcp/handler.py
+++ b/synapse/replication/tcp/handler.py
@@ -56,6 +56,7 @@
     EventsStream,
     FederationStream,
     Stream,
+    ToDeviceStream,
     TypingStream,
 )
 
@@ -115,6 +116,14 @@ def __init__(self, hs):
 
                 continue
 
+            if isinstance(stream, ToDeviceStream):
+                # Only add ToDeviceStream as a source on instances in charge of
+                # sending to device messages.
+                if hs.get_instance_name() in hs.config.worker.writers.to_device:
+                    self._streams_to_replicate.append(stream)
+
+                continue
+
             if isinstance(stream, TypingStream):
                 # Only add TypingStream as a source on the instance in charge of
                 # typing.