diff --git a/api/reviews_api.py b/api/reviews_api.py
index 2c2fc155292a..d6571d4a94bf 100644
--- a/api/reviews_api.py
+++ b/api/reviews_api.py
@@ -26,7 +26,7 @@
 from internals import approval_defs, notifier_helpers
 from internals.core_enums import *
 from internals.core_models import FeatureEntry, Stage
-from internals.review_models import Gate, Vote
+from internals.review_models import Gate, Vote, Amendment, Activity
 
 
 def get_user_feature_and_gate(handler, kwargs) -> Tuple[
@@ -84,7 +84,21 @@ def do_post(self, **kwargs) -> dict[str, str]:
           fe, stage, gate_id)
 
     if new_state in (Vote.REVIEW_REQUESTED, Vote.NA_REQUESTED):
+      old_assignees = gate.assignee_emails[:]
       approval_defs.auto_assign_reviewer(gate)
+      new_assignees = gate.assignee_emails[:]
+      if old_assignees != new_assignees:
+        amendment = Amendment(
+            field_name='review_assignee',
+            old_value=', '.join(old_assignees),
+            new_value=', '.join(new_assignees))
+        activity = Activity(
+            feature_id=fe.key.integer_id(), gate_id=gate_id,
+            author=user.email(), amendments=[amendment])
+        activity.put()
+        # Note: We don't notify assignee about autoassignment, because they
+        # will get a notification of review state change anyway.
+
       notifier_helpers.notify_approvers_of_reviews(
           fe, gate, new_state, user.email())
     else:
diff --git a/internals/notifier_helpers.py b/internals/notifier_helpers.py
index c10c1c2b670e..1e71759cb303 100644
--- a/internals/notifier_helpers.py
+++ b/internals/notifier_helpers.py
@@ -173,6 +173,13 @@ def notify_assignees(
   }
 
   cloud_tasks_helpers.enqueue_task('/tasks/email-assigned', params)
+  amendment = Amendment(
+      field_name='review_assignee',
+      old_value=', '.join(old_assignees), new_value=', '.join(new_assignees))
+  gate_id = gate.key.integer_id()
+  activity = Activity(feature_id=fe.key.integer_id(), gate_id=gate_id,
+                      author=triggering_user_email, amendments=[amendment])
+  activity.put()
 
 
 def notify_subscribers_of_new_comments(fe: 'FeatureEntry', gate: Gate,
diff --git a/internals/review_models.py b/internals/review_models.py
index 6105b8c3b9dc..1328a16fc265 100644
--- a/internals/review_models.py
+++ b/internals/review_models.py
@@ -200,7 +200,7 @@ class Amendment(ndb.Model):
   new_value = ndb.TextProperty()
 
 
-class Activity(ndb.Model):  # copy from Comment
+class Activity(ndb.Model):
   """An activity log entry (comment + amendments) on a gate or feature."""
   feature_id = ndb.IntegerProperty(required=True)
   gate_id = ndb.IntegerProperty()  # The gate commented on, or general comment.