diff --git a/changelog.d/14028.feature b/changelog.d/14028.feature
new file mode 100644
index 0000000000..6f5663a0ef
--- /dev/null
+++ b/changelog.d/14028.feature
@@ -0,0 +1 @@
+The `/relations` endpoint can now be used on workers.
diff --git a/docker/complement/conf/start_for_complement.sh b/docker/complement/conf/start_for_complement.sh
index cc6482f763..bb85d9fed7 100755
--- a/docker/complement/conf/start_for_complement.sh
+++ b/docker/complement/conf/start_for_complement.sh
@@ -57,6 +57,7 @@ if [[ -n "$SYNAPSE_COMPLEMENT_USE_WORKERS" ]]; then
       federation_reader, \
       federation_sender, \
       synchrotron, \
+      client_reader, \
       appservice, \
       pusher"
 
diff --git a/docker/configure_workers_and_start.py b/docker/configure_workers_and_start.py
index 51583dc13d..8e7f605b24 100755
--- a/docker/configure_workers_and_start.py
+++ b/docker/configure_workers_and_start.py
@@ -107,6 +107,33 @@ WORKERS_CONFIG: Dict[str, Dict[str, Any]] = {
         "shared_extra_conf": {},
         "worker_extra_conf": "",
     },
+    "client_reader": {
+        "app": "synapse.app.generic_worker",
+        "listener_resources": ["client"],
+        "endpoint_patterns": [
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/publicRooms$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/joined_members$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/context/.*$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/members$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/state$",
+            "^/_matrix/client/v1/rooms/.*/hierarchy$",
+            "^/_matrix/client/(v1|unstable)/rooms/.*/relations/",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/login$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/account/3pid$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/account/whoami$",
+            "^/_matrix/client/versions$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/voip/turnServer$",
+            "^/_matrix/client/(r0|v3|unstable)/register$",
+            "^/_matrix/client/(r0|v3|unstable)/auth/.*/fallback/web$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/messages$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/event",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/joined_rooms",
+            "^/_matrix/client/(api/v1|r0|v3|unstable/.*)/rooms/.*/aliases",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/search",
+        ],
+        "shared_extra_conf": {},
+        "worker_extra_conf": "",
+    },
     "federation_reader": {
         "app": "synapse.app.generic_worker",
         "listener_resources": ["federation"],
diff --git a/docs/workers.md b/docs/workers.md
index 27041ea57c..e8d6cbaf8b 100644
--- a/docs/workers.md
+++ b/docs/workers.md
@@ -203,6 +203,7 @@ information.
     ^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/members$
     ^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/state$
     ^/_matrix/client/v1/rooms/.*/hierarchy$
+    ^/_matrix/client/(v1|unstable)/rooms/.*/relations/
     ^/_matrix/client/unstable/org.matrix.msc2716/rooms/.*/batch_send$
     ^/_matrix/client/unstable/im.nheko.summary/rooms/.*/summary$
     ^/_matrix/client/(r0|v3|unstable)/account/3pid$
diff --git a/scripts-dev/complement.sh b/scripts-dev/complement.sh
index eab23f18f1..a7b1e1e3a8 100755
--- a/scripts-dev/complement.sh
+++ b/scripts-dev/complement.sh
@@ -126,7 +126,7 @@ export COMPLEMENT_BASE_IMAGE=complement-synapse
 
 extra_test_args=()
 
-test_tags="synapse_blacklist,msc2716,msc3030,msc3787"
+test_tags="synapse_blacklist,msc3787"
 
 # All environment variables starting with PASS_ will be shared.
 # (The prefix is stripped off before reaching the container.)
@@ -158,7 +158,10 @@ else
 
   # We only test faster room joins on monoliths, because they are purposefully
   # being developed without worker support to start with.
-  test_tags="$test_tags,faster_joins"
+  #
+  # The tests for importing historical messages (MSC2716) and jump to date (MSC3030)
+  # also only pass with monoliths, currently.
+  test_tags="$test_tags,faster_joins,msc2716,msc3030"
 fi
 
 
diff --git a/synapse/app/generic_worker.py b/synapse/app/generic_worker.py
index 5e3825fca6..dc49840f73 100644
--- a/synapse/app/generic_worker.py
+++ b/synapse/app/generic_worker.py
@@ -65,6 +65,7 @@ from synapse.rest.client import (
     push_rule,
     read_marker,
     receipts,
+    relations,
     room,
     room_batch,
     room_keys,
@@ -308,6 +309,7 @@ class GenericWorkerServer(HomeServer):
                     sync.register_servlets(self, resource)
                     events.register_servlets(self, resource)
                     room.register_servlets(self, resource, is_worker=True)
+                    relations.register_servlets(self, resource)
                     room.register_deprecated_servlets(self, resource)
                     initial_sync.register_servlets(self, resource)
                     room_batch.register_servlets(self, resource)