diff --git a/autogen/oai/anthropic.py b/autogen/oai/anthropic.py
index 8ed6f909e6bc..4472c177cfdf 100644
--- a/autogen/oai/anthropic.py
+++ b/autogen/oai/anthropic.py
@@ -314,7 +314,7 @@ def oai_messages_to_anthropic_messages(params: Dict[str, Any]) -> list[dict[str,
     last_tool_result_index = -1
     for message in params["messages"]:
         if message["role"] == "system":
-            params["system"] = message["content"]
+            params["system"] = params.get("system", "") + ("\n" if "system" in params else "") + message["content"]
         else:
             # New messages will be added here, manage role alternations
             expected_role = "user" if len(processed_messages) % 2 == 0 else "assistant"