There are daily buses from Athens to Delphi. Buses depart from Liossion KTEL Bus Station in the centre of Athens and need about 3 hours to reach Delphi. To go to Liossion Bus Station, you take the metro line to Attiki Station and then a bus/taxi to KTEL Liossion. The walking time from Attiki to KTEL Liossion is about 30 min. There are also buses to Delphi from many other Greek towns, including Patra and Thessaloniki.
Travel to Delphi by car
Delphi is about 190 km from Athens. To go from Athens to Delphi by car, you follow the National Highway Athens-Lamia and at the junction of Thebes, you turn right following the signs to Levadia. After you pass Levadia, you continue to Arachova and Delphi. Delphi is about 10 km after you pass Arachova.