Three bishops are being treated in hospital for burns, mostly on their faces. A policeman, who ran to help, was also taken to hospital
The 37-year-old priest, who was facing the hearing for alleged drug-related offenses, was arrested unharmed and detained for questioning.
Police said it was not immediately clear what liquid was used, but added that the victims were being treated for burns.
“I express my abhorrence at this unprecedented event,” Greek President Katerina Sakellaropoulou wrote in a tweet after contacting Archbishop Ieronymos, the leader of the Greek church.
Most of the victims hold the senior rank of metropolitan bishop.
Health minister Vassilis Kikilias visited the Athens hospital where the bishops were initially treated, joined by Archbishop Ieronymos.
Mr Ieronymos sad he was “deeply saddened” by the attack but relieved that none of the injuries were considered by doctors to be life-threatening.
Police identified the victims as the metropolitan bishops Antonios of Glyfada, Kyrillos of Kifissia, Kallinikos of Arta, Nikodimos of Kassandra, Dionysios IV of Zakynthos, Dimitrios of Goumenissis, and Andreas of Dryinoupolis.
Additional reporting by the Associated Press.