There are direct overnight trips via ferries departing from Italy (ports of Ancona, Bari, Brindisi or Trieste). For schedule and prices look at the websites of Anek Lines, Minoan Lines, Superfast Ferries.
From Araxos airport which is located 50 Km West of Patras and it is served by several airline companies (e.g.,Ryanair, LTU, TUIfly, SkyExpress, etc), especially in the period May to October. From Araxos, you can reach Patras either by bus, or by taxi (approx. 40-50 Euros).
From Athens International Airport "Eleftherios Venizelos" which is located 250 Km East of Patras. There are regular flights connecting Athens to most European cities.
Several car rental agencies operate on the airport. The new “Attiki Odos” high-speed toll motorway connects the airport with Athens and the main greek highways. Leave the airport following initially the signs to ATHINA and then to ELEFSINA to enter “Attiki Odos”. From that point on just stay on the highway following the signs to ELEFSINA, subsequenty to KORINTHOS, and finally to PATRA. After Korinthos, the highway splits into two and you must follow the right way (there are signs to PATRA). The total distance between Athens airport and Patras is about 250km. To reach Patras, take the exit “PATRA-CENTRE / PORT”, and then follow the signs to “Port”.
The “Proastiakos” (suburban) railway, operated by “Trainose”, connects Athens airport to the railway network of the rest of Greece operated by the “OSE” company. You can take the train from the airport with direction to Peiraias port and then change at railway station «Kato Acharnai» to line Piraeus – Athens – Kiato with direction to Kiato. At the Kiato station passengers, with final destination Patras, transfer to buses serving the Kiato-Patras line. Trainose bus services operate between Kiato and Patras (and vice versa) due to ongoing infrastructure works on the railway line between those two stations. The current timetable can be seen here.
The “KTEL Achaias” intercity bus company has regular buses to Patras. You must first get to the Kifisos Bus Station . You can get there from the airport, either by taxi or by taking the X93 express bus (24-hour service) that departs just outside the airport terminal at the Arrival level. The bus stop is next to Arrival Exit 5. You can buy ticket on the bus. Either way it takes about 60 min to get there, and the bus runs approximately every 30 minutes 24 hours a day, seven days a week (X93 timetable). Kifisos Bus Station is the last stop of X93.
From Kifisos Bus Station there is a bus to Patra almost every 30 minutes (current schedule). The first bus departs around 05:30 and the last one around 22:30. Trip time is around 3 hours 10 minutes (or 2 hours 40 minutes for an “express” bus). You must buy a ticket before boarding. There is a big ticket hall at the east side of the station. Head for the booth with the signs “Achaia” and/or “Patra”. There is no need to reserve tickets in advance, you will usually find a ticket for a bus leaving in the next hour. Ask at the ticket booth for directions on how to find the proper bus.