diff --git a/litellm/llms/chatgpt/responses/transformation.py b/litellm/llms/chatgpt/responses/transformation.py
index 9774b762396..b191d6d101b 100644
--- a/litellm/llms/chatgpt/responses/transformation.py
+++ b/litellm/llms/chatgpt/responses/transformation.py
@@ -104,6 +104,7 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
             "tools",
             "tool_choice",
             "reasoning",
+            "prompt_cache_key",
             "previous_response_id",
             "truncation",
         }
diff --git a/tests/unit/llms/chatgpt/responses/test_chatgpt_responses_transformation.py b/tests/unit/llms/chatgpt/responses/test_chatgpt_responses_transformation.py
index 0b04dd0ed78..b02d1f58cc0 100644
--- a/tests/unit/llms/chatgpt/responses/test_chatgpt_responses_transformation.py
+++ b/tests/unit/llms/chatgpt/responses/test_chatgpt_responses_transformation.py
@@ -169,6 +169,7 @@ class TestChatGPTResponsesAPITransformation:
                 "max_output_tokens": 123,
                 "stream_options": {"include_usage": True},
                 # supported and should be preserved
+                "prompt_cache_key": "session_123",
                 "truncation": "auto",
                 "previous_response_id": "resp_123",
                 "reasoning": {"effort": "medium"},
@@ -187,6 +188,7 @@ class TestChatGPTResponsesAPITransformation:
         assert "max_output_tokens" not in request
         assert "stream_options" not in request
 
+        assert request["prompt_cache_key"] == "session_123"
         assert request["truncation"] == "auto"
         assert request["previous_response_id"] == "resp_123"
         assert request["reasoning"] == {"effort": "medium"}