Ithaca sits immediately east of Kefalonia, close enough that the crossing is one of the shortest in Greece. The useful decisions here are which port you leave from and whether you bring the car, not how long it takes.
Diagram by Greece Trips. Free to reuse with credit - CC BY 4.0.
Which port
Two on the Kefalonia side, and they suit different trips.
Sami, on the east coast, is the main one and the more frequent. Fiskardo, the pastel harbour village at the northern tip, also has crossings, and it is the prettier place to sail from and to wait in.
On the Ithaca side the boats land at Piso Aetos, a functional quay in the middle of the island, or at Vathy, the capital on its deep harbour. Which one matters: Piso Aetos has essentially nothing at it, so arriving there without transport is awkward.
Check which port pair your sailing uses in both directions before booking anything on the far side.
Take the car
The single most useful decision. The crossing takes vehicles, and Ithaca is a narrow, mountainous island where the villages are spread along one winding road and public transport is thin.
If you already have a car on Kefalonia, bring it. If you do not, consider whether a day on Ithaca without one gets you much beyond Vathy.
Which islands need a car covers the general rule; on Ithaca the answer is yes.
What is actually there
Worth setting expectations, because Ithaca disappoints people who arrive expecting a monument. It is the quietest of the three main southern Ionian islands: a narrow mountainous island with a deep harbour at Vathy, a hilltop village at Anogi, a small northern village at Stavros, and very little development.
The Homeric associations are carried lightly and there is no great site to visit. What there is instead is swimming, a couple of good harbours and almost nobody, which is precisely why people who like it like it a great deal.
Season, and the wind
Sailings are frequent in high summer and thin out either side of it. The Ionian is more sheltered than the Aegean and cancellations are less common than on the Cycladic lines, but they happen.
Check the last boat back before you commit to an afternoon on the far side, which is the standing rule on every short crossing.
Diagram by Greece Trips. Free to reuse with credit - CC BY 4.0.
Where this leaves you
One of the shortest hops in Greece, from Sami or from Fiskardo, landing at Piso Aetos or Vathy. Take the car if you have one, because Ithaca is strung along a winding road and Piso Aetos is a quay with nothing at it. Expect quiet and swimming rather than sights, and check which ports your sailing actually uses in both directions.
Quick answers
How long is the ferry from Kefalonia to Ithaca?
It is one of the shortest crossings in Greece, though the exact duration depends on which port pair your sailing uses and on the operator. Check the current schedule rather than relying on a printed figure.
Which port do you leave from?
Sami on Kefalonia’s east coast is the main one and the most frequent. Fiskardo at the northern tip also has crossings and is the prettier place to sail from. On the Ithaca side, boats land at Piso Aetos or at Vathy.
Should you take a car to Ithaca?
Yes, if you have one. Ithaca is narrow and mountainous with villages strung along a winding road and thin public transport, and one of the landing points, Piso Aetos, has essentially nothing at it.
What is there to do on Ithaca?
Not a great deal, which is the appeal. There is a deep harbour at Vathy, a hilltop village at Anogi, a small northern village at Stavros, good swimming and very little development. The Homeric connection is carried lightly and there is no major site.