diff --git a/vllm/entrypoints/openai/serving_engine.py b/vllm/entrypoints/openai/serving_engine.py
index 8ce4ff574699d..30b8499b08d5b 100644
--- a/vllm/entrypoints/openai/serving_engine.py
+++ b/vllm/entrypoints/openai/serving_engine.py
@@ -1375,6 +1375,8 @@ class OpenAIServing:
                     for tool_call in tool_call_info.tool_calls
                 )
                 content = tool_call_info.content
+                if content and content.strip() == "":
+                    content = None
             else:
                 # No tool calls.
                 return None, content