diff --git a/deepnote_toolkit/sql/sql_execution.py b/deepnote_toolkit/sql/sql_execution.py
index 77ea872..2710c06 100644
--- a/deepnote_toolkit/sql/sql_execution.py
+++ b/deepnote_toolkit/sql/sql_execution.py
@@ -117,6 +117,7 @@ class ExecuteSqlError(Exception):
 
         _handle_iam_params(sql_alchemy_dict)
         _handle_federated_auth_params(sql_alchemy_dict)
+        _handle_mssql_trusted_connection(sql_alchemy_dict)
 
         requires_bigquery_oauth = (
             sql_alchemy_dict["url"] == "bigquery://?user_supplied_client=true"
@@ -351,6 +352,38 @@ def _handle_federated_auth_params(sql_alchemy_dict: dict[str, Any]) -> None:
         )
 
 
+def _handle_mssql_trusted_connection(sql_alchemy_dict: dict[str, Any]) -> None:
+    """Handle MS SQL Server Windows Authentication (trusted connections) in-place.
+
+    When 'mssql_trusted_connection' is True in params, removes username and password
+    from the connection URL to enable Windows Authentication via pymssql.
+    """
+    params = sql_alchemy_dict.get("params", {})
+
+    if not params.get("mssql_trusted_connection"):
+        return
+
+    url_obj = make_url(sql_alchemy_dict["url"])
+
+    if not url_obj.drivername.startswith("mssql"):
+        logger.warning(
+            "mssql_trusted_connection is only supported for MS SQL Server connections"
+        )
+        return
+
+    # Build new URL without username/password for Windows Authentication
+    new_url = URL.create(
+        drivername=url_obj.drivername,
+        host=url_obj.host,
+        port=url_obj.port,
+        database=url_obj.database,
+        query=url_obj.query,
+    )
+
+    sql_alchemy_dict["url"] = str(new_url)
+    del params["mssql_trusted_connection"]
+
+
 @contextlib.contextmanager
 def _create_sql_ssh_uri(ssh_enabled, sql_alchemy_dict):
     server = None
diff --git a/tests/unit/test_sql_execution.py b/tests/unit/test_sql_execution.py
index de46ba4..69b35f5 100644
--- a/tests/unit/test_sql_execution.py
+++ b/tests/unit/test_sql_execution.py
@@ -940,3 +940,88 @@ def test_federated_auth_params_bigquery_missing_params(
 
         # Verify the dict was not modified
         self.assertEqual(sql_alchemy_dict, original_dict)
+
+
+class TestMssqlTrustedConnection(unittest.TestCase):
+    """Tests for MS SQL Server Windows Authentication (trusted connections)."""
+
+    def test_trusted_connection_removes_credentials(self):
+        """Test that mssql_trusted_connection removes username and password from URL."""
+        from deepnote_toolkit.sql.sql_execution import _handle_mssql_trusted_connection
+
+        sql_alchemy_dict = {
+            "url": "mssql+pymssql://user:password@myserver:1433/mydb",
+            "params": {"mssql_trusted_connection": True},
+        }
+
+        _handle_mssql_trusted_connection(sql_alchemy_dict)
+
+        # Verify credentials were removed from URL
+        self.assertIn("mssql+pymssql://", sql_alchemy_dict["url"])
+        self.assertIn("myserver", sql_alchemy_dict["url"])
+        self.assertIn("mydb", sql_alchemy_dict["url"])
+        self.assertNotIn("user", sql_alchemy_dict["url"])
+        self.assertNotIn("password", sql_alchemy_dict["url"])
+
+        # Verify the flag was removed from params
+        self.assertNotIn("mssql_trusted_connection", sql_alchemy_dict["params"])
+
+    def test_trusted_connection_preserves_query_params(self):
+        """Test that existing query parameters are preserved."""
+        from deepnote_toolkit.sql.sql_execution import _handle_mssql_trusted_connection
+
+        sql_alchemy_dict = {
+            "url": "mssql+pymssql://user:password@myserver/mydb?charset=utf8",
+            "params": {"mssql_trusted_connection": True},
+        }
+
+        _handle_mssql_trusted_connection(sql_alchemy_dict)
+
+        # Verify query params are preserved
+        self.assertIn("charset=utf8", sql_alchemy_dict["url"])
+
+    def test_trusted_connection_not_enabled(self):
+        """Test that no action is taken when mssql_trusted_connection is not set."""
+        from deepnote_toolkit.sql.sql_execution import _handle_mssql_trusted_connection
+
+        sql_alchemy_dict = {
+            "url": "mssql+pymssql://user:password@myserver/mydb",
+            "params": {},
+        }
+        original_url = sql_alchemy_dict["url"]
+
+        _handle_mssql_trusted_connection(sql_alchemy_dict)
+
+        self.assertEqual(sql_alchemy_dict["url"], original_url)
+
+    def test_trusted_connection_false(self):
+        """Test that no action is taken when mssql_trusted_connection is False."""
+        from deepnote_toolkit.sql.sql_execution import _handle_mssql_trusted_connection
+
+        sql_alchemy_dict = {
+            "url": "mssql+pymssql://user:password@myserver/mydb",
+            "params": {"mssql_trusted_connection": False},
+        }
+        original_url = sql_alchemy_dict["url"]
+
+        _handle_mssql_trusted_connection(sql_alchemy_dict)
+
+        self.assertEqual(sql_alchemy_dict["url"], original_url)
+
+    @mock.patch("deepnote_toolkit.sql.sql_execution.logger")
+    def test_trusted_connection_non_mssql_url_warns(self, mock_logger):
+        """Test that a warning is logged for non-mssql URLs."""
+        from deepnote_toolkit.sql.sql_execution import _handle_mssql_trusted_connection
+
+        sql_alchemy_dict = {
+            "url": "postgresql://user:password@localhost/db",
+            "params": {"mssql_trusted_connection": True},
+        }
+        original_url = sql_alchemy_dict["url"]
+
+        _handle_mssql_trusted_connection(sql_alchemy_dict)
+
+        mock_logger.warning.assert_called_once_with(
+            "mssql_trusted_connection is only supported for MS SQL Server connections"
+        )
+        self.assertEqual(sql_alchemy_dict["url"], original_url)