diff --git a/src/magentic/chat_model/mistral_chat_model.py b/src/magentic/chat_model/mistral_chat_model.py
index cd9009b3..8b6a3a18 100644
--- a/src/magentic/chat_model/mistral_chat_model.py
+++ b/src/magentic/chat_model/mistral_chat_model.py
@@ -42,6 +42,11 @@ def _get_tool_choice(  # type: ignore[override]
         """
         return openai.NOT_GIVEN if allow_string_output else _MistralToolChoice.ANY.value
 
+    def _get_parallel_tool_calls(
+        self, *, tools_specified: bool, output_types: Iterable[type]
+    ) -> bool | openai.NotGiven:
+        return openai.NOT_GIVEN
+
 
 R = TypeVar("R")
 
diff --git a/src/magentic/chat_model/openai_chat_model.py b/src/magentic/chat_model/openai_chat_model.py
index b366b712..5ea82e0f 100644
--- a/src/magentic/chat_model/openai_chat_model.py
+++ b/src/magentic/chat_model/openai_chat_model.py
@@ -435,6 +435,19 @@ def _get_tool_choice(
             return tool_schemas[0].as_tool_choice()
         return "required"
 
+    def _get_parallel_tool_calls(
+        self, *, tools_specified: bool, output_types: Iterable[type]
+    ) -> bool | openai.NotGiven:
+        if not tools_specified:  # Enforced by OpenAI API
+            return openai.NOT_GIVEN
+        if self.api_type == "azure":
+            return openai.NOT_GIVEN
+        if is_any_origin_subclass(output_types, ParallelFunctionCall):
+            return openai.NOT_GIVEN
+        if is_any_origin_subclass(output_types, AsyncParallelFunctionCall):
+            return openai.NOT_GIVEN
+        return False
+
     @overload
     def complete(
         self,
@@ -496,6 +509,9 @@ def complete(
             tool_choice=self._get_tool_choice(
                 tool_schemas=tool_schemas, allow_string_output=allow_string_output
             ),
+            parallel_tool_calls=self._get_parallel_tool_calls(
+                tools_specified=bool(tool_schemas), output_types=output_types
+            ),
         )
         usage_ref, response = _create_usage_ref(response)
 
@@ -607,6 +623,9 @@ async def acomplete(
             tool_choice=self._get_tool_choice(
                 tool_schemas=tool_schemas, allow_string_output=allow_string_output
             ),
+            parallel_tool_calls=self._get_parallel_tool_calls(
+                tools_specified=bool(tool_schemas), output_types=output_types
+            ),
         )
         usage_ref, response = _create_usage_ref_async(response)