Samosir is reached by ferry from Parapat on the eastern shore of Lake Toba. Parapat is about 4.5 hours by bus from Medan, the major city in North Sumatra, and the main point of arrival for most visitors coming overland from the north. Buses run regularly from Medan's Amplas bus terminal. From Parapat, ferries cross to Tuk Tuk on Samosir approximately every hour during the day; the crossing takes about 30 minutes.
A second approach is via Ajibata, close to Parapat, from which car ferries operate to Tomok and Ambarita — useful if you are bringing a vehicle. The island can also be reached by the road bridge connecting Pangururan on the western side of Samosir to the Sumatran mainland.
From Medan's airport (Kualanamu, KNO), the journey to Parapat takes around 4–5 hours depending on traffic. Some visitors travelling between Medan and Berastagi include a Lake Toba detour on their northern Sumatra circuit.