diff --git a/langfuse/_client/utils.py b/langfuse/_client/utils.py
index 16d963d88..2ef187507 100644
--- a/langfuse/_client/utils.py
+++ b/langfuse/_client/utils.py
@@ -59,6 +59,7 @@ def span_formatter(span: ReadableSpan) -> str:
                 "instrumentationScope": instrumentationScope,
             },
             indent=2,
+            ensure_ascii=False,
         )
         + "\n"
     )
diff --git a/langfuse/_utils/serializer.py b/langfuse/_utils/serializer.py
index 1350ea00c..f88ae9566 100644
--- a/langfuse/_utils/serializer.py
+++ b/langfuse/_utils/serializer.py
@@ -37,6 +37,7 @@ class Serializable:  # type: ignore
 
 class EventSerializer(JSONEncoder):
     def __init__(self, *args: Any, **kwargs: Any) -> None:
+        kwargs.setdefault("ensure_ascii", False)
         super().__init__(*args, **kwargs)
         self.seen: set[int] = set()  # Track seen objects to detect circular references