diff --git a/langchain/chat_models/openai.py b/langchain/chat_models/openai.py
index 1b035fba..a4d2ac87 100644
--- a/langchain/chat_models/openai.py
+++ b/langchain/chat_models/openai.py
@@ -143,10 +143,24 @@ class ChatOpenAI(BaseChatModel):
 
         extra = values.get("model_kwargs", {})
         for field_name in list(values):
+            if field_name in extra:
+                raise ValueError(f"Found {field_name} supplied twice.")
             if field_name not in all_required_field_names:
-                if field_name in extra:
-                    raise ValueError(f"Found {field_name} supplied twice.")
+                logger.warning(
+                    f"""WARNING! {field_name} is not default parameter.
+                    {field_name} was transferred to model_kwargs.
+                    Please confirm that {field_name} is what you intended."""
+                )
                 extra[field_name] = values.pop(field_name)
+
+        disallowed_model_kwargs = all_required_field_names | {"model"}
+        invalid_model_kwargs = disallowed_model_kwargs.intersection(extra.keys())
+        if invalid_model_kwargs:
+            raise ValueError(
+                f"Parameters {invalid_model_kwargs} should be specified explicitly. "
+                f"Instead they were passed in as part of `model_kwargs` parameter."
+            )
+
         values["model_kwargs"] = extra
         return values
 
diff --git a/langchain/llms/openai.py b/langchain/llms/openai.py
index b29cbf60..bfca7fe3 100644
--- a/langchain/llms/openai.py
+++ b/langchain/llms/openai.py
@@ -186,15 +186,24 @@ class BaseOpenAI(BaseLLM):
 
         extra = values.get("model_kwargs", {})
         for field_name in list(values):
+            if field_name in extra:
+                raise ValueError(f"Found {field_name} supplied twice.")
             if field_name not in all_required_field_names:
-                if field_name in extra:
-                    raise ValueError(f"Found {field_name} supplied twice.")
                 logger.warning(
                     f"""WARNING! {field_name} is not default parameter.
-                    {field_name} was transfered to model_kwargs.
+                    {field_name} was transferred to model_kwargs.
                     Please confirm that {field_name} is what you intended."""
                 )
                 extra[field_name] = values.pop(field_name)
+
+        disallowed_model_kwargs = all_required_field_names | {"model"}
+        invalid_model_kwargs = disallowed_model_kwargs.intersection(extra.keys())
+        if invalid_model_kwargs:
+            raise ValueError(
+                f"Parameters {invalid_model_kwargs} should be specified explicitly. "
+                f"Instead they were passed in as part of `model_kwargs` parameter."
+            )
+
         values["model_kwargs"] = extra
         return values
 
@@ -422,7 +431,7 @@ class BaseOpenAI(BaseLLM):
     def prep_streaming_params(self, stop: Optional[List[str]] = None) -> Dict[str, Any]:
         """Prepare the params for streaming."""
         params = self._invocation_params
-        if params["best_of"] != 1:
+        if "best_of" in params and params["best_of"] != 1:
             raise ValueError("OpenAI only supports best_of == 1 for streaming")
         if stop is not None:
             if "stop" in params:
diff --git a/tests/integration_tests/chat_models/test_openai.py b/tests/integration_tests/chat_models/test_openai.py
index 432c2c88..679cb06c 100644
--- a/tests/integration_tests/chat_models/test_openai.py
+++ b/tests/integration_tests/chat_models/test_openai.py
@@ -147,3 +147,27 @@ async def test_async_chat_openai_streaming() -> None:
             assert isinstance(generation, ChatGeneration)
             assert isinstance(generation.text, str)
             assert generation.text == generation.message.content
+
+
+def test_chat_openai_extra_kwargs() -> None:
+    """Test extra kwargs to chat openai."""
+    # Check that foo is saved in extra_kwargs.
+    llm = ChatOpenAI(foo=3, max_tokens=10)
+    assert llm.max_tokens == 10
+    assert llm.model_kwargs == {"foo": 3}
+
+    # Test that if extra_kwargs are provided, they are added to it.
+    llm = ChatOpenAI(foo=3, model_kwargs={"bar": 2})
+    assert llm.model_kwargs == {"foo": 3, "bar": 2}
+
+    # Test that if provided twice it errors
+    with pytest.raises(ValueError):
+        ChatOpenAI(foo=3, model_kwargs={"foo": 2})
+
+    # Test that if explicit param is specified in kwargs it errors
+    with pytest.raises(ValueError):
+        ChatOpenAI(model_kwargs={"temperature": 0.2})
+
+    # Test that "model" cannot be specified in kwargs
+    with pytest.raises(ValueError):
+        ChatOpenAI(model_kwargs={"model": "text-davinci-003"})
diff --git a/tests/integration_tests/llms/test_openai.py b/tests/integration_tests/llms/test_openai.py
index e10a9c0b..5132e3bb 100644
--- a/tests/integration_tests/llms/test_openai.py
+++ b/tests/integration_tests/llms/test_openai.py
@@ -34,6 +34,14 @@ def test_openai_extra_kwargs() -> None:
     with pytest.raises(ValueError):
         OpenAI(foo=3, model_kwargs={"foo": 2})
 
+    # Test that if explicit param is specified in kwargs it errors
+    with pytest.raises(ValueError):
+        OpenAI(model_kwargs={"temperature": 0.2})
+
+    # Test that "model" cannot be specified in kwargs
+    with pytest.raises(ValueError):
+        OpenAI(model_kwargs={"model": "text-davinci-003"})
+
 
 def test_openai_llm_output_contains_model_name() -> None:
     """Test llm_output contains model_name."""