diff --git a/litellm/proxy/management_endpoints/model_management_endpoints.py b/litellm/proxy/management_endpoints/model_management_endpoints.py
index 18e07c09bff..e465b76ba18 100644
--- a/litellm/proxy/management_endpoints/model_management_endpoints.py
+++ b/litellm/proxy/management_endpoints/model_management_endpoints.py
@@ -548,6 +548,17 @@ async def _update_existing_team_model_assignment(
                 http_request=Request(scope={"type": "http"}),
                 user_api_key_dict=user_api_key_dict,
             )
+    elif not old_public_name and public_model_name:
+        # First-time assignment of public name on an existing team deployment:
+        # ensure the team's models list is updated so team routing can resolve it.
+        await team_model_add(
+            data=TeamModelAddRequest(
+                team_id=team_id,
+                models=[public_model_name],
+            ),
+            http_request=Request(scope={"type": "http"}),
+            user_api_key_dict=user_api_key_dict,
+        )
 
     patch_data.model_name = None
 
diff --git a/tests/test_litellm/proxy/management_endpoints/test_model_management_endpoints.py b/tests/test_litellm/proxy/management_endpoints/test_model_management_endpoints.py
index 63dd164d700..3da360e84d2 100644
--- a/tests/test_litellm/proxy/management_endpoints/test_model_management_endpoints.py
+++ b/tests/test_litellm/proxy/management_endpoints/test_model_management_endpoints.py
@@ -629,8 +629,6 @@ class TestTeamModelSiblingRouting:
         team_id = "team_no_alias"
         public_name = "gpt-4.1-mini"
 
-        mock_update_team = AsyncMock()
-
         async def mock_add_model_to_db(model_params, user_api_key_dict, prisma_client):
             return MagicMock(model_id=str(uuid.uuid4()))
 
@@ -650,9 +648,6 @@ class TestTeamModelSiblingRouting:
                 model_info=ModelInfo(team_id=team_id),
             )
             with patch(
-                "litellm.proxy.management_endpoints.model_management_endpoints.update_team",
-                mock_update_team,
-            ), patch(
                 "litellm.proxy.management_endpoints.model_management_endpoints._add_model_to_db",
                 side_effect=mock_add_model_to_db,
             ), patch(
@@ -665,7 +660,6 @@ class TestTeamModelSiblingRouting:
                     prisma_client=prisma_client,
                 )
 
-        mock_update_team.assert_not_called()
         assert mock_team_model_add.call_count == 2
 
     @pytest.mark.asyncio
@@ -801,8 +795,6 @@ class TestTeamModelUpdate:
             "litellm.proxy.proxy_server.premium_user",
             True,
         ), patch(
-            "litellm.proxy.management_endpoints.model_management_endpoints.update_team"
-        ) as mock_update_team, patch(
             "litellm.proxy.management_endpoints.model_management_endpoints.team_model_add"
         ) as mock_team_model_add:
             result = await _update_team_model_in_db(
@@ -814,8 +806,6 @@ class TestTeamModelUpdate:
 
             assert result.get("model_name", "").startswith("model_name_test_team_123_")
             assert "team_public_model_name" in str(result.get("model_info", ""))
-            # update_team must not be called (no model_aliases writes for team models)
-            mock_update_team.assert_not_called()
             # team_model_add must be called to add public name to team's models list
             mock_team_model_add.assert_called_once()
 
@@ -879,6 +869,47 @@ class TestTeamModelUpdate:
             # team_model_add should be called to add new public name
             mock_add.assert_called_once()
 
+    @pytest.mark.asyncio
+    async def test_first_time_public_name_assignment_adds_team_model(self):
+        """If existing team deployment had no public name, first assignment must call team_model_add."""
+        from litellm.proxy.management_endpoints.model_management_endpoints import (
+            _update_existing_team_model_assignment,
+        )
+        from litellm.types.router import ModelInfo
+
+        db_model = Deployment(
+            model_name="model_name_team_123_uuid1",
+            litellm_params=LiteLLM_Params(model="azure/gpt-4o-mini"),
+            model_info=ModelInfo(team_id="team_123"),
+        )
+
+        patch_data = updateDeployment(
+            model_name="new-public-name",
+            model_info=ModelInfo(team_id="team_123"),
+        )
+
+        user_api_key_dict = UserAPIKeyAuth(
+            user_id="test_user",
+            user_role=LitellmUserRoles.PROXY_ADMIN,
+        )
+
+        with patch(
+            "litellm.proxy.management_endpoints.model_management_endpoints.team_model_delete"
+        ) as mock_delete, patch(
+            "litellm.proxy.management_endpoints.model_management_endpoints.team_model_add"
+        ) as mock_add:
+            await _update_existing_team_model_assignment(
+                team_id="team_123",
+                public_model_name="new-public-name",
+                db_model=db_model,
+                patch_data=patch_data,
+                user_api_key_dict=user_api_key_dict,
+                prisma_client=None,
+            )
+
+            mock_add.assert_called_once()
+            mock_delete.assert_not_called()
+
     @pytest.mark.asyncio
     async def test_rename_handles_legacy_string_model_info(self):
         """Test rename path handles legacy string-encoded model_info rows without crashing."""