diff --git a/src/openai/lib/_parsing/_responses.py b/src/openai/lib/_parsing/_responses.py
index 81e6b2b983..033e06e6ed 100644
--- a/src/openai/lib/_parsing/_responses.py
+++ b/src/openai/lib/_parsing/_responses.py
@@ -61,7 +61,7 @@ def parse_response(
     for output in response.output or []:
         if output.type == "message":
             content_list: List[ParsedContent[TextFormatT]] = []
-            for item in output.content:
+            for item in output.content or []:
                 if item.type != "output_text":
                     content_list.append(item)
                     continue
diff --git a/tests/lib/responses/test_null_content.py b/tests/lib/responses/test_null_content.py
new file mode 100644
index 0000000000..9c492fae8b
--- /dev/null
+++ b/tests/lib/responses/test_null_content.py
@@ -0,0 +1,100 @@
+from __future__ import annotations
+
+import json
+
+import httpx2
+import pytest
+
+from openai import OpenAI, AsyncOpenAI
+
+
+def _null_content_item() -> dict[str, object]:
+    return {
+        "id": "msg_test",
+        "type": "message",
+        "role": "assistant",
+        "status": "completed",
+        "content": None,
+    }
+
+
+def _completed_event(output: object) -> dict[str, object]:
+    return {
+        "type": "response.completed",
+        "sequence_number": 1,
+        "response": {
+            "id": "resp_test",
+            "status": "completed",
+            "model": "test-model",
+            "output": output,
+        },
+    }
+
+
+def _stream_body(output: object) -> bytes:
+    events: list[dict[str, object]] = [
+        {"type": "response.created", "sequence_number": 0, "response": {"id": "resp_test", "status": "in_progress"}},
+        _completed_event(output),
+    ]
+    return "".join(f"data: {json.dumps(event)}\n\n" for event in events).encode()
+
+
+@pytest.mark.parametrize("sync", [True, False], ids=["sync", "async"])
+async def test_stream_explicit_null_message_content(sync: bool) -> None:
+    """An explicit completed output whose message has content:null must parse to empty content, not TypeError."""
+    transport = httpx2.MockTransport(
+        lambda _request: httpx2.Response(
+            200, content=_stream_body([_null_content_item()]), headers={"content-type": "text/event-stream"}
+        )
+    )
+    if sync:
+        with OpenAI(api_key="fake-test-key", http_client=httpx2.Client(transport=transport)) as client:
+            with client.responses.stream(model="test-model", input="test") as stream:
+                list(stream)
+                final = stream.get_final_response()
+    else:
+        async with AsyncOpenAI(
+            api_key="fake-test-key", http_client=httpx2.AsyncClient(transport=transport)
+        ) as async_client:
+            async with async_client.responses.stream(model="test-model", input="test") as async_stream:
+                [event async for event in async_stream]
+                final = await async_stream.get_final_response()
+
+    assert len(final.output) == 1
+    message = final.output[0]
+    assert message.type == "message"
+    assert message.content == []
+
+
+@pytest.mark.parametrize("sync", [True, False], ids=["sync", "async"])
+async def test_parse_null_message_content(sync: bool) -> None:
+    """Non-streaming responses.parse must not raise TypeError on content:null either."""
+    body = json.dumps(
+        {
+            "id": "resp_test",
+            "object": "response",
+            "created_at": 1,
+            "model": "test-model",
+            "status": "completed",
+            "parallel_tool_calls": False,
+            "tool_choice": "auto",
+            "tools": [],
+            "output": [_null_content_item()],
+        }
+    )
+    transport = httpx2.MockTransport(
+        lambda _request: httpx2.Response(200, content=body, headers={"content-type": "application/json"})
+    )
+    if sync:
+        with OpenAI(api_key="fake-test-key", http_client=httpx2.Client(transport=transport)) as client:
+            parsed = client.responses.parse(model="test-model", input="test")
+    else:
+        async with AsyncOpenAI(
+            api_key="fake-test-key", http_client=httpx2.AsyncClient(transport=transport)
+        ) as async_client:
+            parsed = await async_client.responses.parse(model="test-model", input="test")
+
+    assert len(parsed.output) == 1
+    message = parsed.output[0]
+    assert message.type == "message"
+    assert message.content == []