diff --git a/sdks/python/tests/unit/evaluation/metrics/test_is_json.py b/sdks/python/tests/unit/evaluation/metrics/test_is_json.py
new file mode 100644
index 00000000000..205cd3cf88d
--- /dev/null
+++ b/sdks/python/tests/unit/evaluation/metrics/test_is_json.py
@@ -0,0 +1,41 @@
+import pytest
+
+from opik.evaluation.metrics import IsJson
+from opik.evaluation.metrics.score_result import ScoreResult
+
+
+@pytest.mark.parametrize(
+    "output",
+    [
+        '{"key": "value"}',
+        "[1, 2, 3]",
+        "5",
+        '"a json string"',
+        "true",
+        "null",
+    ],
+)
+def test_is_json__valid_json__returns_score_1(output):
+    metric = IsJson(track=False)
+
+    assert metric.score(output=output) == ScoreResult(
+        name=metric.name, value=1.0, reason=None, metadata=None
+    )
+
+
+@pytest.mark.parametrize(
+    "output",
+    [
+        "Not a JSON string",
+        "",
+        '{"key": "value"',
+        None,
+        123,
+    ],
+)
+def test_is_json__invalid_json__returns_score_0(output):
+    metric = IsJson(track=False)
+
+    assert metric.score(output=output) == ScoreResult(
+        name=metric.name, value=0.0, reason=None, metadata=None
+    )