You can get to Kefalonia by ferry boat or aircraft.
Trips by ferry boat (as for all the islands of the Ionian) start from the harbors of Patra and Kyllini. They are carried out on a daily basis throughout the year and are multiplied in summer. You can also get to Kefalonia from the neighbouring islands if you have a mind to do some island hopping. The islands of Ithaca, Zakynthos, Kerkyra (Corfu), Lefkada, and Astakos as well as a direct ferry boat link from Italy.
Three basic routes exist by ferry boat:
Patra to Sami (3hrs 30min)
Kyllini to Poro (2hrs 30min)
Astakos to Agia Efimia
Schinari (Shinari) Zakynthos to Pessada or Poros (1hr)
Italy to Sami
The duration of the journey of course is dependent every time on how many harbors the ferry will visit.
There are also daily flights from the international airport of Athens Eleftherios Venizelos to Kefalonia. The duration of these flights is 45 minutes and during the summer there are many more chartered flights from various areas of Europe directly to Kefalonia.
And finally, you can get to Argostoli by bus which starts at Athens and travels via Patra or Kyllini which finally reaches the harbours of Sami or Poros or Argostoli.
For more information on bookings call the following numbers:
Athens KTEL: 210 5129498
Argostoli KTEL: 26710 22281