diff --git a/libs/partners/ollama/langchain_ollama/chat_models.py b/libs/partners/ollama/langchain_ollama/chat_models.py
index 8fa1c967db4..0b672d1e343 100644
--- a/libs/partners/ollama/langchain_ollama/chat_models.py
+++ b/libs/partners/ollama/langchain_ollama/chat_models.py
@@ -741,26 +741,30 @@ class ChatOllama(BaseChatModel):
         if self.stop is not None:
             stop = self.stop
 
-        options_dict = kwargs.pop(
-            "options",
-            {
-                "mirostat": self.mirostat,
-                "mirostat_eta": self.mirostat_eta,
-                "mirostat_tau": self.mirostat_tau,
-                "num_ctx": self.num_ctx,
-                "num_gpu": self.num_gpu,
-                "num_thread": self.num_thread,
-                "num_predict": self.num_predict,
-                "repeat_last_n": self.repeat_last_n,
-                "repeat_penalty": self.repeat_penalty,
-                "temperature": self.temperature,
-                "seed": self.seed,
-                "stop": self.stop if stop is None else stop,
-                "tfs_z": self.tfs_z,
-                "top_k": self.top_k,
-                "top_p": self.top_p,
-            },
-        )
+        options_dict = kwargs.pop("options", None)
+        if options_dict is None:
+            # Only include parameters that are explicitly set (not None)
+            options_dict = {
+                k: v
+                for k, v in {
+                    "mirostat": self.mirostat,
+                    "mirostat_eta": self.mirostat_eta,
+                    "mirostat_tau": self.mirostat_tau,
+                    "num_ctx": self.num_ctx,
+                    "num_gpu": self.num_gpu,
+                    "num_thread": self.num_thread,
+                    "num_predict": self.num_predict,
+                    "repeat_last_n": self.repeat_last_n,
+                    "repeat_penalty": self.repeat_penalty,
+                    "temperature": self.temperature,
+                    "seed": self.seed,
+                    "stop": self.stop if stop is None else stop,
+                    "tfs_z": self.tfs_z,
+                    "top_k": self.top_k,
+                    "top_p": self.top_p,
+                }.items()
+                if v is not None
+            }
 
         params = {
             "messages": ollama_messages,
diff --git a/libs/partners/ollama/tests/unit_tests/test_chat_models.py b/libs/partners/ollama/tests/unit_tests/test_chat_models.py
index d5708a4937a..8719fdc3bd4 100644
--- a/libs/partners/ollama/tests/unit_tests/test_chat_models.py
+++ b/libs/partners/ollama/tests/unit_tests/test_chat_models.py
@@ -24,7 +24,7 @@ MODEL_NAME = "llama3.1"
 
 @contextmanager
 def _mock_httpx_client_stream(
-    *args: Any, **kwargs: Any
+    *_args: Any, **_kwargs: Any
 ) -> Generator[Response, Any, Any]:
     yield Response(
         status_code=200,
@@ -310,3 +310,103 @@ def test_load_response_with_actual_content_is_not_skipped(
         assert result.content == "This is actual content"
         assert result.response_metadata.get("done_reason") == "load"
         assert not caplog.text
+
+
+def test_none_parameters_excluded_from_options() -> None:
+    """Test that None parameters are excluded from the options dict sent to Ollama."""
+    response = [
+        {
+            "model": "test-model",
+            "created_at": "2025-01-01T00:00:00.000000000Z",
+            "done": True,
+            "done_reason": "stop",
+            "message": {"role": "assistant", "content": "Hello!"},
+        }
+    ]
+
+    with patch("langchain_ollama.chat_models.Client") as mock_client_class:
+        mock_client = MagicMock()
+        mock_client_class.return_value = mock_client
+        mock_client.chat.return_value = response
+
+        # Create ChatOllama with only num_ctx set
+        llm = ChatOllama(model="test-model", num_ctx=4096)
+        llm.invoke([HumanMessage("Hello")])
+
+        # Verify that chat was called
+        assert mock_client.chat.called
+
+        # Get the options dict that was passed to chat
+        call_kwargs = mock_client.chat.call_args[1]
+        options = call_kwargs.get("options", {})
+
+        # Only num_ctx should be in options, not None parameters
+        assert "num_ctx" in options
+        assert options["num_ctx"] == 4096
+
+        # These parameters should NOT be in options since they were None
+        assert "mirostat" not in options
+        assert "mirostat_eta" not in options
+        assert "mirostat_tau" not in options
+        assert "tfs_z" not in options
+
+
+def test_all_none_parameters_results_in_empty_options() -> None:
+    """Test that when all parameters are None, options dict is empty."""
+    response = [
+        {
+            "model": "test-model",
+            "created_at": "2025-01-01T00:00:00.000000000Z",
+            "done": True,
+            "done_reason": "stop",
+            "message": {"role": "assistant", "content": "Hello!"},
+        }
+    ]
+
+    with patch("langchain_ollama.chat_models.Client") as mock_client_class:
+        mock_client = MagicMock()
+        mock_client_class.return_value = mock_client
+        mock_client.chat.return_value = response
+
+        # Create ChatOllama with no parameters set
+        llm = ChatOllama(model="test-model")
+        llm.invoke([HumanMessage("Hello")])
+
+        # Get the options dict that was passed to chat
+        call_kwargs = mock_client.chat.call_args[1]
+        options = call_kwargs.get("options", {})
+
+        # Options should be empty when no parameters are set
+        assert options == {}
+
+
+def test_explicit_options_dict_preserved() -> None:
+    """Test that explicitly provided options dict is preserved and not filtered."""
+    response = [
+        {
+            "model": "test-model",
+            "created_at": "2025-01-01T00:00:00.000000000Z",
+            "done": True,
+            "done_reason": "stop",
+            "message": {"role": "assistant", "content": "Hello!"},
+        }
+    ]
+
+    with patch("langchain_ollama.chat_models.Client") as mock_client_class:
+        mock_client = MagicMock()
+        mock_client_class.return_value = mock_client
+        mock_client.chat.return_value = response
+
+        llm = ChatOllama(model="test-model")
+        # Pass explicit options dict, including None values
+        llm.invoke(
+            [HumanMessage("Hello")],
+            options={"temperature": 0.5, "custom_param": None},
+        )
+
+        # Get the options dict that was passed to chat
+        call_kwargs = mock_client.chat.call_args[1]
+        options = call_kwargs.get("options", {})
+
+        # Explicit options should be preserved as-is
+        assert options == {"temperature": 0.5, "custom_param": None}