diff --git a/litellm/utils.py b/litellm/utils.py
index 7732cd88cb5..d28b9cb03a0 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -7973,7 +7973,12 @@ def cleanup_none_field_in_message(message: AllMessageValues):
     remove None fields in the message - e.g. {"function": None} - some providers raise validation errors
     """
     new_message: Final = message.copy()
-    return {k: v for k, v in new_message.items() if v is not None}
+    return {
+        k: v
+        for k, v in new_message.items()
+        if v is not None
+        or (k == "content" and new_message.get("role") == "assistant" and new_message.get("tool_calls"))
+    }
 
 
 def validate_chat_completion_user_messages(messages: list[AllMessageValues]):
diff --git a/tests/test_litellm/test_message_normalization.py b/tests/test_litellm/test_message_normalization.py
new file mode 100644
index 00000000000..9483ade4637
--- /dev/null
+++ b/tests/test_litellm/test_message_normalization.py
@@ -0,0 +1,33 @@
+from litellm.utils import cleanup_none_field_in_message
+
+
+def test_cleanup_preserves_null_content_for_assistant_tool_calls():
+    message = {
+        "role": "assistant",
+        "content": None,
+        "tool_calls": [
+            {
+                "id": "call_1",
+                "type": "function",
+                "function": {"name": "get_weather", "arguments": "{}"},
+            }
+        ],
+    }
+
+    result = cleanup_none_field_in_message(message)
+
+    assert result == message
+    assert "content" in result
+
+
+def test_cleanup_still_removes_unneeded_null_fields():
+    message = {
+        "role": "assistant",
+        "content": None,
+        "tool_calls": None,
+        "function_call": None,
+    }
+
+    result = cleanup_none_field_in_message(message)
+
+    assert result == {"role": "assistant"}