diff --git a/haystack/components/generators/chat/openai.py b/haystack/components/generators/chat/openai.py
index 251b0b741c..0b699e3bc1 100644
--- a/haystack/components/generators/chat/openai.py
+++ b/haystack/components/generators/chat/openai.py
@@ -286,12 +286,13 @@ def _prepare_api_call(  # noqa: PLR0913
         tools_strict = tools_strict if tools_strict is not None else self.tools_strict
         _check_duplicate_tool_names(tools)
 
-        openai_tools = None
+        openai_tools = {}
         if tools:
-            openai_tools = [
+            tool_definitions = [
                 {"type": "function", "function": {**t.tool_spec, **({"strict": tools_strict} if tools_strict else {})}}
                 for t in tools
             ]
+            openai_tools = {"tools": tool_definitions}
 
         is_streaming = streaming_callback is not None
         num_responses = generation_kwargs.pop("n", 1)
@@ -302,8 +303,8 @@ def _prepare_api_call(  # noqa: PLR0913
             "model": self.model,
             "messages": openai_formatted_messages,  # type: ignore[arg-type] # openai expects list of specific message types
             "stream": streaming_callback is not None,
-            "tools": openai_tools,  # type: ignore[arg-type]
             "n": num_responses,
+            **openai_tools,
             **generation_kwargs,
         }
 
diff --git a/releasenotes/notes/do-not-pass-tools-to-openai-if-none-1fe09e924e7fad7a.yaml b/releasenotes/notes/do-not-pass-tools-to-openai-if-none-1fe09e924e7fad7a.yaml
new file mode 100644
index 0000000000..aa309098fa
--- /dev/null
+++ b/releasenotes/notes/do-not-pass-tools-to-openai-if-none-1fe09e924e7fad7a.yaml
@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    OpenAIChatGenerator no longer passes tools to the OpenAI client if none are provided.
+    Previously, a null value was passed.
+    This change improves compatibility with OpenAI-compatible APIs that do not support tools.
diff --git a/test/components/generators/chat/test_openai.py b/test/components/generators/chat/test_openai.py
index 8333608ea6..eb50d92739 100644
--- a/test/components/generators/chat/test_openai.py
+++ b/test/components/generators/chat/test_openai.py
@@ -293,6 +293,9 @@ def test_run_with_params(self, chat_messages, openai_mock_chat_completion):
         assert kwargs["max_tokens"] == 10
         assert kwargs["temperature"] == 0.5
 
+        # check that the tools are not passed to the OpenAI API (the generator is initialized without tools)
+        assert "tools" not in kwargs
+
         # check that the component returns the correct response
         assert isinstance(response, dict)
         assert "replies" in response
@@ -400,9 +403,14 @@ def test_run_with_tools(self, tools):
 
             mock_chat_completion_create.return_value = completion
 
-            component = OpenAIChatGenerator(api_key=Secret.from_token("test-api-key"), tools=tools)
+            component = OpenAIChatGenerator(api_key=Secret.from_token("test-api-key"), tools=tools, tools_strict=True)
             response = component.run([ChatMessage.from_user("What's the weather like in Paris?")])
 
+        # ensure that the tools are passed to the OpenAI API
+        assert mock_chat_completion_create.call_args[1]["tools"] == [
+            {"type": "function", "function": {**tools[0].tool_spec, "strict": True}}
+        ]
+
         assert len(response["replies"]) == 1
         message = response["replies"][0]