diff --git a/sagemaker-core/src/sagemaker/core/local/local_session.py b/sagemaker-core/src/sagemaker/core/local/local_session.py
index 9d6ab7b199..363585c1d1 100644
--- a/sagemaker-core/src/sagemaker/core/local/local_session.py
+++ b/sagemaker-core/src/sagemaker/core/local/local_session.py
@@ -670,8 +670,8 @@ def _initialize(
             validate_sagemaker_config(sagemaker_config)
 
         if self.s3_endpoint_url is not None:
-            self.s3_resource = boto_session.resource("s3", endpoint_url=self.s3_endpoint_url)
-            self.s3_client = boto_session.client("s3", endpoint_url=self.s3_endpoint_url)
+            self.s3_resource = self.boto_session.resource("s3", endpoint_url=self.s3_endpoint_url)
+            self.s3_client = self.boto_session.client("s3", endpoint_url=self.s3_endpoint_url)
             self.sagemaker_config = (
                 sagemaker_config
                 if sagemaker_config
diff --git a/sagemaker-core/tests/unit/local/test_local_session.py b/sagemaker-core/tests/unit/local/test_local_session.py
index 91f4e4feaa..d20706d1b9 100644
--- a/sagemaker-core/tests/unit/local/test_local_session.py
+++ b/sagemaker-core/tests/unit/local/test_local_session.py
@@ -509,6 +509,26 @@ def test_local_session_with_s3_endpoint(self):
 
                 assert session.s3_endpoint_url == "http://localhost:9000"
 
+    @patch("boto3.Session")
+    def test_local_session_with_s3_endpoint_and_default_boto_session(self, mock_boto_session_class):
+        """Test custom S3 endpoint when no boto session is passed in"""
+        mock_boto_session = Mock()
+        mock_boto_session.region_name = "us-west-2"
+        mock_boto_session_class.return_value = mock_boto_session
+
+        with patch("sagemaker.core.local.local_session.load_sagemaker_config", return_value={}):
+            with patch(
+                "sagemaker.core.local.local_session.load_local_mode_config",
+                return_value={"local": {}},
+            ):
+                session = LocalSession(s3_endpoint_url="http://localhost:9000")
+
+        mock_boto_session.resource.assert_called_once_with(
+            "s3", endpoint_url="http://localhost:9000"
+        )
+        mock_boto_session.client.assert_any_call("s3", endpoint_url="http://localhost:9000")
+        assert session.s3_resource is mock_boto_session.resource.return_value
+
     @patch("boto3.Session")
     def test_local_session_no_region_raises(self, mock_boto_session_class):
         """Test that missing region raises error"""