diff --git a/src/sentry/auth_v2/endpoints/auth_merge_user_accounts.py b/src/sentry/auth_v2/endpoints/auth_merge_user_accounts.py
index d9eb83aa4b6f51..8dc4c04a79c341 100644
--- a/src/sentry/auth_v2/endpoints/auth_merge_user_accounts.py
+++ b/src/sentry/auth_v2/endpoints/auth_merge_user_accounts.py
@@ -7,13 +7,14 @@
 from sentry.api.base import control_silo_endpoint
 from sentry.api.paginator import OffsetPaginator
 from sentry.api.serializers import serialize
+from sentry.api.serializers.rest_framework.base import CamelSnakeSerializer
 from sentry.auth_v2.endpoints.base import AuthV2Endpoint
 from sentry.users.api.serializers.user import UserSerializerWithOrgMemberships
 from sentry.users.models.user import User
 from sentry.users.models.user_merge_verification_code import UserMergeVerificationCode
 
 
-class AuthMergeUserAccountsValidator(serializers.Serializer):
+class AuthMergeUserAccountsValidator(CamelSnakeSerializer):
     verification_code = serializers.CharField(required=True)
     ids_to_merge = serializers.ListField(child=serializers.IntegerField(), required=True)
     ids_to_delete = serializers.ListField(child=serializers.IntegerField(), required=True)
@@ -104,4 +105,4 @@ def post(self, request: Request) -> Response:
             user.merge_to(primary_user)
             user.delete()
 
-        return Response("Successfully merged user accounts.")
+        return Response(serialize([primary_user], request.user, UserSerializerWithOrgMemberships()))
diff --git a/src/sentry/users/api/serializers/user.py b/src/sentry/users/api/serializers/user.py
index bdf45bff1da35d..7f99578e1d1570 100644
--- a/src/sentry/users/api/serializers/user.py
+++ b/src/sentry/users/api/serializers/user.py
@@ -430,19 +430,19 @@ def get_attrs(
         memberships = OrganizationMemberMapping.objects.filter(
             user_id__in={u.id for u in item_list}
         ).values_list("user_id", "organization_id", named=True)
-        active_org_id_to_name = dict(
+        active_org_id_to_slug = dict(
             OrganizationMapping.objects.filter(
                 organization_id__in={m.organization_id for m in memberships},
                 status=OrganizationStatus.ACTIVE,
-            ).values_list("organization_id", "name")
+            ).values_list("organization_id", "slug")
         )
-        active_organization_ids = active_org_id_to_name.keys()
+        active_organization_ids = active_org_id_to_slug.keys()
 
-        user_org_memberships: DefaultDict[int, list[str]] = defaultdict(list)
+        user_org_memberships: DefaultDict[int, set[str]] = defaultdict(set)
         for membership in memberships:
             if membership.organization_id in active_organization_ids:
-                user_org_memberships[membership.user_id].append(
-                    active_org_id_to_name[membership.organization_id]
+                user_org_memberships[membership.user_id].add(
+                    active_org_id_to_slug[membership.organization_id]
                 )
         for item in item_list:
             attrs[item]["organizations"] = user_org_memberships[item.id]