diff --git a/sdk/evaluation/azure-ai-evaluation/azure/ai/evaluation/_aoai/python_grader.py b/sdk/evaluation/azure-ai-evaluation/azure/ai/evaluation/_aoai/python_grader.py
index ccc1d87fb639..f5884a7ec2a8 100644
--- a/sdk/evaluation/azure-ai-evaluation/azure/ai/evaluation/_aoai/python_grader.py
+++ b/sdk/evaluation/azure-ai-evaluation/azure/ai/evaluation/_aoai/python_grader.py
@@ -30,8 +30,8 @@ class AzureOpenAIPythonGrader(AzureOpenAIGrader):
         ~azure.ai.evaluation.OpenAIModelConfiguration]
     :param name: The name of the grader.
     :type name: str
-    :param image_tag: The image tag for the Python execution environment.
-    :type image_tag: str
+    :param image_tag: The image tag for the Python execution environment. Defaults to "2025-05-08".
+    :type image_tag: Optional[str]
     :param pass_threshold: Score threshold for pass/fail classification. Scores >= threshold are considered passing.
     :type pass_threshold: float
     :param source: Python source code containing the grade function.
@@ -63,7 +63,7 @@ def __init__(
         name: str,
         pass_threshold: float,
         source: str,
-        image_tag: Optional[str] = None,
+        image_tag: Optional[str] = "2025-05-08",
         credential: Optional[TokenCredential] = None,
         **kwargs: Any,
     ):
diff --git a/sdk/evaluation/azure-ai-evaluation/tests/unittests/test_aoai_python_grader.py b/sdk/evaluation/azure-ai-evaluation/tests/unittests/test_aoai_python_grader.py
index 48e69a0ac14f..ad5aeded70a5 100644
--- a/sdk/evaluation/azure-ai-evaluation/tests/unittests/test_aoai_python_grader.py
+++ b/sdk/evaluation/azure-ai-evaluation/tests/unittests/test_aoai_python_grader.py
@@ -52,3 +52,28 @@ def test_invalid_pass_threshold(self):
                 pass_threshold=1.5,
                 source=source_code,
             )
+
+    def test_default_image_tag(self):
+        """Test that image_tag has a default value of '2025-05-08'."""
+        model_config = AzureOpenAIModelConfiguration(
+            azure_endpoint="https://test.openai.azure.com",
+            api_key="test-key",
+            azure_deployment="test-deployment",
+        )
+
+        source_code = """
+def grade(sample: dict, item: dict) -> float:
+    return 1.0
+"""
+
+        # Create grader without specifying image_tag
+        grader = AzureOpenAIPythonGrader(
+            model_config=model_config,
+            name="python_test",
+            pass_threshold=0.5,
+            source=source_code,
+        )
+
+        # Verify the grader was created successfully
+        assert grader.pass_threshold == 0.5
+        assert grader.id == "azureai://built-in/evaluators/azure-openai/python_grader"