diff --git a/tests/test_litellm/llms/vertex_ai/rerank/test_vertex_ai_rerank_transformation.py b/tests/test_litellm/llms/vertex_ai/rerank/test_vertex_ai_rerank_transformation.py
index c1de7933f9..fbf5239797 100644
--- a/tests/test_litellm/llms/vertex_ai/rerank/test_vertex_ai_rerank_transformation.py
+++ b/tests/test_litellm/llms/vertex_ai/rerank/test_vertex_ai_rerank_transformation.py
@@ -15,9 +15,30 @@ from litellm.types.rerank import RerankResponse
 
 class TestVertexAIRerankTransform:
     def setup_method(self):
+        # Save and clear Google/Vertex AI environment variables to prevent
+        # test isolation issues where previous tests leave credentials set
+        self._saved_env = {}
+        env_vars_to_clear = [
+            "GOOGLE_APPLICATION_CREDENTIALS",
+            "GOOGLE_CLOUD_PROJECT",
+            "VERTEXAI_PROJECT",
+            "VERTEX_PROJECT",
+            "VERTEX_LOCATION",
+            "VERTEX_AI_PROJECT",
+        ]
+        for var in env_vars_to_clear:
+            if var in os.environ:
+                self._saved_env[var] = os.environ[var]
+                del os.environ[var]
+
         self.config = VertexAIRerankConfig()
         self.model = "semantic-ranker-default@latest"
 
+    def teardown_method(self):
+        # Restore saved environment variables
+        for var, value in self._saved_env.items():
+            os.environ[var] = value
+
     @patch('litellm.llms.vertex_ai.rerank.transformation.VertexAIRerankConfig._ensure_access_token')
     def test_get_complete_url(self, mock_ensure_access_token):
         """Test URL generation for Vertex AI Discovery Engine rerank API."""