diff --git a/python/langsmith/evaluation/_runner.py b/python/langsmith/evaluation/_runner.py
index 6a7f3ab3d..2ab94700c 100644
--- a/python/langsmith/evaluation/_runner.py
+++ b/python/langsmith/evaluation/_runner.py
@@ -647,16 +647,20 @@ def evaluate_comparative(
         ...         },
         ...     )
         ...     tool_args = completion.choices[0].message.tool_calls[0].function.arguments
-        ...     preference = json.loads(tool_args)["preferred_option"]
+        ...     loaded_args = json.loads(tool_args)
+        ...     preference = loaded_args["preferred_option"]
+        ...     comment = loaded_args["reasoning"]
         ...     if preference == "A":
         ...         return {
         ...             "key": "ranked_preference",
         ...             "scores": {runs[0].id: 1, runs[1].id: 0},
+        ...             "comment": comment,
         ...         }
         ...     else:
         ...         return {
         ...             "key": "ranked_preference",
         ...             "scores": {runs[0].id: 0, runs[1].id: 1},
+        ...             "comment": comment,
         ...         }
         >>> def score_length_difference(runs: list, example: schemas.Example):
         ...     # Just return whichever response is longer.
@@ -781,12 +785,18 @@ def evaluate_and_submit_feedback(
             result = comparator.compare_runs(runs_list, example)
             if client is None:
                 raise ValueError("Client is required to submit feedback.")
+        comments = (
+            {str(rid): result.comment for rid in result.scores}
+            if isinstance(result.comment, str)
+            else (result.comment or {})
+        )
         for run_id, score in result.scores.items():
             executor.submit(
                 client.create_feedback,
                 run_id=run_id,
                 key=result.key,
                 score=score,
+                comment=comments.get(str(run_id)),
                 comparative_experiment_id=comparative_experiment.id,
                 source_run_id=result.source_run_id,
                 feedback_group_id=feedback_group_id,
diff --git a/python/langsmith/evaluation/evaluator.py b/python/langsmith/evaluation/evaluator.py
index feb0e95e4..668f99e9d 100644
--- a/python/langsmith/evaluation/evaluator.py
+++ b/python/langsmith/evaluation/evaluator.py
@@ -158,6 +158,9 @@ class ComparisonEvaluationResult(BaseModel):
     """The scores for each run in the comparison."""
     source_run_id: Optional[Union[uuid.UUID, str]] = None
     """The ID of the trace of the evaluator itself."""
+    comment: Optional[Union[str, Dict[Union[uuid.UUID, str], str]]] = None
+    """Comment for the scores. If a string, it's shared across all target runs.
+    If a dict, it maps run IDs to individual comments."""
 
 
 _COMPARISON_OUTPUT = Union[ComparisonEvaluationResult, dict]