The town was founded in ancient times. The Greek geographer Pausanias in his book “Messiniaka” reports the original location of Koroni at today’s Petalidi, a town a few kilometers north of Koroni. He also reports many temples of Greek gods and a copper statue of Zeus.
Because of reorderings, in the centuries that followed the town of Koroni moved to its current location where the ancient town of Asini had once stood. In the 6th and 7th centuries AD, the Byzantines built a fortress there. It appears for the first time as a bishopric in the Notitiae Episcopatuum of the Byzantine Emperor Leo VI the Wise, in which it appears as a suffragan of the See of Patras.
Surviving seals give the names of some of its Greek bishops. The Greek eparchy was suppressed in the 19th century as part of an ecclesiastical reorganization after Greece gained its independence.