In the spring of 1454 he was consecrated by the metropolitan of Heraclea Perinthus, but, since both the Church of Hagia Sophia and the palace of the patriarch were now in the hands of the Ottomans, he took up his residence successively in two monasteries of the city. While holding the episcopal office Gennadius drew up, apparently for the use of Mehmed, a confession or exposition of the Christian faith, which was translated into Turkish by Ahmed, Qadi of Berrhoea (and first printed by A. Brassicanus at Vienna in 1530).