Born Pedros Keshishian in Beirut, Lebanon in 1947. He was ordained priest in 1968, and was consecrated bishop in Antelias on 22 August 1980. From 1980 to 1995 he was Primate of Lebanon at the head of the Armenian Prelacy of Lebanon, part of the Catholicossate of the Great House of Cilicia, a Holy See of the Armenian Apostolic Church.

In 1991 he became moderator of the Central Committee of the World Council of Churches and also serves on the Middle East Council of Churches.