Which Tallinn Ferry to Take
West Harbour or Katajanokka
This is the decision. West Harbour (Länsisatama) Terminal 2 sits in Jätkäsaari, west of the centre, and both Tallink Silja and Eckerö Line sail from it, with check-in inside the terminal. Katajanokka is east of the centre, is served by trams 4 and 5, and is where Viking Line sails from. If your hotel is on the eastern side, Katajanokka will save you twenty minutes each way; if it is anywhere west or central, West Harbour is easier. Neither is near Market Square, and I have redirected more people from that square to a ferry terminal than I can count.
Frequency
Tallink Silja runs 5 to 7 crossings a day and therefore gives you the most control over a day trip — an early out, a late back, and something to fall onto if you miss one. Viking Line runs 2 to 3 a day and Eckerö Line 1 to 3. Around ten crossings a day run in total. For a day trip where the hours in the city are the whole point, frequency is worth more than anything else on the comparison sheet.
The ships
All three lines run large modern ferries with restaurants and shops on board, and on a day-trip ticket a seat is included. Crossing times are 2 h 15 to 2 h 30 with Eckerö Line and 2 h 15 to 2 h 45 with Viking Line, with the fast Tallink Silja sailings at about two hours; the whole spread across all ships runs up to about 3 hours 25. Nobody should choose a line over fifteen minutes. The crossing time page has the detail.
The product most people actually book
A return day-trip ferry ticket with Tallink Silja from West Harbour Terminal 2, on Megastar or MyStar, with check-in inside the terminal, a seat included and up to about 9.5 hours in Tallinn. It is unguided — you walk off, you walk into the Old Town, you come back. That suits most people; if you want a guided day, this is not it. See the Tallinn day trip page and what to avoid once you are there.
Practicalities
Both countries are in the EU and the Schengen area and share a currency. There is no hard border, but carriers check identity, so carry a passport or ID card. Check-in is inside the terminal building, not at the ship, and it closes before departure — treat it like a short-haul flight rather than like a tram.
Choose your line by which terminal you can reach quickly on the morning of the trip. On a day this long, twenty minutes at each end is worth more than any difference between the ships.
Frequently asked questions
Which ferry line is best from Helsinki to Tallinn?
They are comparable. Tallink Silja has the most departures from West Harbour Terminal 2; Viking Line sails from Katajanokka, which suits the eastern side of the city.
Where does the Tallinn ferry leave from in Helsinki?
Tallink Silja and Eckerö Line from West Harbour (Länsisatama) Terminal 2; Viking Line from Katajanokka.
Is the Tallinn ferry guided?
No. A return day-trip ticket is transport only — you walk into the Old Town by yourself. See what is there.