diff --git a/tests/entrypoints/openai/test_chat.py b/tests/entrypoints/openai/test_chat.py
index 8d13f64dce01c..843d15e768093 100644
--- a/tests/entrypoints/openai/test_chat.py
+++ b/tests/entrypoints/openai/test_chat.py
@@ -899,19 +899,19 @@ async def test_response_format_json_schema(client: openai.AsyncOpenAI):
 
 
 @pytest.mark.asyncio
-async def test_extra_fields(client: openai.AsyncOpenAI):
-    with pytest.raises(BadRequestError) as exc_info:
-        await client.chat.completions.create(
-            model=MODEL_NAME,
-            messages=[{
-                "role": "system",
-                "content": "You are a helpful assistant.",
-                "extra_field": "0",
-            }],  # type: ignore
-            temperature=0,
-            seed=0)
-
-    assert "extra_forbidden" in exc_info.value.message
+async def test_extra_fields_allowed(client: openai.AsyncOpenAI):
+    resp = await client.chat.completions.create(
+        model=MODEL_NAME,
+        messages=[{
+            "role": "user",
+            "content": "what is 1+1?",
+            "extra_field": "0",
+        }],  # type: ignore
+        temperature=0,
+        seed=0)
+
+    content = resp.choices[0].message.content
+    assert content is not None
 
 
 @pytest.mark.asyncio
diff --git a/vllm/entrypoints/openai/protocol.py b/vllm/entrypoints/openai/protocol.py
index b7b064ae01f05..a82212677f63a 100644
--- a/vllm/entrypoints/openai/protocol.py
+++ b/vllm/entrypoints/openai/protocol.py
@@ -9,12 +9,15 @@
 from typing_extensions import Annotated
 
 from vllm.entrypoints.chat_utils import ChatCompletionMessageParam
+from vllm.logger import init_logger
 from vllm.pooling_params import PoolingParams
 from vllm.sampling_params import (BeamSearchParams, GuidedDecodingParams,
                                   RequestOutputKind, SamplingParams)
 from vllm.sequence import Logprob
 from vllm.utils import random_uuid
 
+logger = init_logger(__name__)
+
 # torch is mocked during docs generation,
 # so we have to provide the values as literals
 _MOCK_LONG_INFO = Namespace(min=-9223372036854775808, max=9223372036854775807)
@@ -35,8 +38,19 @@
 
 
 class OpenAIBaseModel(BaseModel):
-    # OpenAI API does not allow extra fields
-    model_config = ConfigDict(extra="forbid")
+    # OpenAI API does allow extra fields
+    model_config = ConfigDict(extra="allow")
+
+    @model_validator(mode="before")
+    @classmethod
+    def __log_extra_fields__(cls, data):
+        if isinstance(data, dict):
+            extra_fields = data.keys() - cls.model_fields.keys()
+            if extra_fields:
+                logger.warning(
+                    "The following fields were present in the request "
+                    "but ignored: %s", extra_fields)
+        return data
 
 
 class ErrorResponse(OpenAIBaseModel):