diff --git a/py/src/braintrust/logger.py b/py/src/braintrust/logger.py
index 41dbb027..8d7e4cf2 100644
--- a/py/src/braintrust/logger.py
+++ b/py/src/braintrust/logger.py
@@ -3557,7 +3557,7 @@ def _validate_and_sanitize_experiment_log_partial_args(event: Mapping[str, Any])
 
             if not isinstance(score, (int, float)):
                 raise ValueError("score values must be numbers")
-            if score < 0 or score > 1:
+            if not 0 <= score <= 1:
                 raise ValueError("score values must be between 0 and 1")
 
     if "metadata" in sanitized_event and sanitized_event["metadata"] is not None:
diff --git a/py/src/braintrust/score.py b/py/src/braintrust/score.py
index c9395c49..614ac818 100644
--- a/py/src/braintrust/score.py
+++ b/py/src/braintrust/score.py
@@ -45,7 +45,7 @@ def as_dict(self):
         }
 
     def __post_init__(self):
-        if self.score is not None and (self.score < 0 or self.score > 1):
+        if self.score is not None and not 0 <= self.score <= 1:
             raise ValueError(f"score ({self.score}) must be between 0 and 1")
         if self.error is not None:
             warnings.warn(
diff --git a/py/src/braintrust/test_logger.py b/py/src/braintrust/test_logger.py
index 9bb585fa..df380a8f 100644
--- a/py/src/braintrust/test_logger.py
+++ b/py/src/braintrust/test_logger.py
@@ -3829,3 +3829,16 @@ def test_proxy_conn_base_url(proxy_url, expected_base_url):
     state = BraintrustState()
     state.proxy_url = proxy_url
     assert state.proxy_conn().base_url == expected_base_url
+
+
+@pytest.mark.parametrize("value", [float("nan"), float("inf"), float("-inf")])
+def test_log_score_validation_rejects_nonfinite_values(value):
+    # Exercise validation without constructing a logger or making requests.
+    with pytest.raises(ValueError, match="between 0 and 1"):
+        logger._validate_and_sanitize_experiment_log_partial_args({"scores": {"accuracy": value}})
+
+
+@pytest.mark.parametrize("value", [None, 0, 0.5, 1, False, True])
+def test_log_score_validation_preserves_valid_values(value):
+    result = logger._validate_and_sanitize_experiment_log_partial_args({"scores": {"accuracy": value}})
+    assert result["scores"]["accuracy"] == value
diff --git a/py/src/braintrust/test_score.py b/py/src/braintrust/test_score.py
index 77cca41b..28013151 100644
--- a/py/src/braintrust/test_score.py
+++ b/py/src/braintrust/test_score.py
@@ -135,6 +135,14 @@ def test_score_validation_enforces_bounds(self):
         with self.assertRaises(ValueError):
             Score(name="invalid_over_one", score=1.1)
 
+    def test_score_rejects_nonfinite_values(self):
+        for value in (float("nan"), float("inf"), float("-inf")):
+            with self.subTest(value=value):
+                with self.assertRaises(ValueError):
+                    Score(name="nonfinite", score=value)
+                with self.assertRaises(ValueError):
+                    Score.from_dict({"name": "nonfinite", "score": value})
+
     def test_score_does_not_include_deprecated_error_field(self):
         """Test that as_dict() does not include the deprecated error field."""
         score = Score(name="test_scorer", score=0.5)