Dionysius was born in Dimitsana, in the Peloponnese. He became a monk and entered in a monastery in Constantinople where he was a pupil of Mark, Archbishop of Ephesus, who ordained him as priest. During the Fall of Constantinople in 1453 he was enslaved by the Ottomans, but he was bought and freed some time later in Adrianople by an archon known as Kyritzes (probably Demetrios Apokaukos, one of the two Greek secretaries of Sultan Mehmed II).