How far in advance should one book ferry tickets for travel between the islands?

Just to clarify: You will be a foot passenger, not taking a vehicle with you?

Correct, foot only.

Depends on when you are going and where.

If you are going during the High Season and to the Over-the-Top Greek Islands you may want to book in advance otherwise you can buy your ferry ticket the same day you are traveling.

However, with COVID I doubt they'll be huge crowds lining up for a ferry.

If you do buy in advance I would book directly with the ferry company rather than a third-party

@tommyk5 Sure, I meant normally under non-Covid conditions. Not during necessarily the high season, but spring or fall.

As foot passengers in May or September we’ve never had problems booking on the day. Sometimes we book the night before to save queuing on the morning but I’ve never been on a ferry at that time of year when people weren’t buying tickets 5 minutes before departure.

Alan

My wife is Greek so since we retired we spend 3-4 weeks in Greece every year except this year. We never buy ferry tickets in advance. Most of the time we buy the tickets just before boarding. Sometimes we buy tickets the day before just to avoid dealing with potential lines. The big slow ferries always have room available. Fast ferries with numbered seats could possibly sellout on popular routes, but we have never experienced them being sold out the day before.

Just adding to what has already been said. We buy our ferry tickets while we are on an island. Often it is the day before we sail sometimes a couple of days before. The advantage of booking when you are on an island is the local travel agents have the latest information about weather strikes and cancellations. Stuff does happen when you travel so up to date information is important.

I do use ferry web sites during my trip planning stage to search island connections and ferry sailing times but we always purchase in person at the ferry ticket office or from a local travel agent.

Always bought just prior to boarding even during busy times.