diff --git a/src/google/adk/evaluation/evaluation_generator.py b/src/google/adk/evaluation/evaluation_generator.py
index e0e61fe758..c1e3227a29 100644
--- a/src/google/adk/evaluation/evaluation_generator.py
+++ b/src/google/adk/evaluation/evaluation_generator.py
@@ -672,6 +672,12 @@ def convert_events_to_eval_invocations(
               events_to_add.append(event)
               break
 
+      # Skip invocations without user content — evaluations without
+      # user input are not meaningful and would cause a Pydantic
+      # ValidationError on Invocation.user_content.
+      if not (user_content and user_content.parts):
+        continue
+
       invocation_events = [
           InvocationEvent(author=e.author, content=e.content)
           for e in events_to_add