Born Petros Manuk in Sivas (Sebaste) in Anatolia on 7 February 1676, he entered the Surp Nshan (Holy Cross) monastery, taking the name Mekhitar. In 1696 he was ordained a priest.
in 1701 inspired by the idea of creating an order of preachers dedicated to raising the educational and spiritual level of the Armenian people Mekhitar founded in Constantinople what would become known after his death as the Mekhitarist Order. , Two years later, escaping persecution by the Ottoman authorities, the order moved to Modon in the Peloponnese, then known as the Morea, which was a Venetian possession. In 1715, the order moved to the Island of San Lazzaro degli Armeni at the invitation of the Venetian Republic. Mekhitar built up the monastery on the island and the order which sent out priests to serve Armenian communities in the Middle East.
Mekhitar died at the monastery on 27 April 1749 and is buried in the monastery church.