Sareyn is 29 km west of Ardabil along a good two-lane road that climbs slowly into the Alborz foothills. Shared taxis (savari) leave from Ardabil's western terminal whenever they have four passengers — the fare is small and the trip takes about half an hour. There is no train.
The nearest airport is Ardabil, served by daily flights from Tehran and less frequent connections to Mashhad. From the airport, a private taxi to Sareyn costs roughly the same as a meal in a good restaurant. If you arrive by long-distance bus from Tehran or Tabriz you will be dropped in Ardabil and need to continue from there.