The attack took place during a disciplinary hearing against the 36-year-old priest on Wednesday afternoon, according to police.
Three bishops are being treated in hospital for the burns, mostly on their faces.
A policeman, who ran to help the bishops, was also taken to hospital.
The suspect, a priest who risked being expelled from the church, was accused of being involved in drug trafficking, according to the ANA press agency.
The bishops were meeting to discuss defrocking him – stripping him of his priesthood – after he was allegedly discovered to be in possession of 1.8 grams of cocaine in June 2018, according to local media.
The priest had brought “large bottle of corrosive liquid” to the session at the Petraki Monastery in central Athens, newspaper Ta Nea reported.
A guard, who managed to catch the priest at the gate of the monastery, also suffered burns and was taken to hospital.
Health Minister Vassilis Kikilias visited the victims in hospital and said one would be transferred for plastic surgery.