Greek Railways (OSE) operates a train from Athens to Eretria every 4 hours. Tickets cost $4 - $5 and the journey takes 46 min. Alternatively, KTEL Evias operates a bus from Athens to Eretria hourly, and the journey takes 1 h 20 min. KTEL Evias also services this route every 3 hours.
From Athens train to Sfendali then taxi to Eretria. 1 h 27 min 58€. From Athens - KTEL Liosion bus to Chalcis then bus to Eretria. 2 h 56 min. From Athens taxi to Eretria. 1 h 7 min 93€. From Athens drive to Eretria. 1 h 7 min 14€.