Information from the Synaxarion mention that Alexander was originally from Calabria in Italy and his parents were George and Vryaine. From very young he was given to God and stayed in a Monastery, where he cultivated virtue and became a good labourer of God’s commands. He was granted divine visions, while for twenty days he stayed completelyfasting. But he also stayed naked for four years and fell into thousands of problems because of attacks of the Saracens. In this way, he lived many years travelling around Greece with his pupils Vitalius and Nicephorus.

He was elected as a vicar to assist the aged bishop Saint Metrophanes of Constantinople. As a result, both he and Metrophanes are both reported as being the first Bishop of Constantinople (both are also sometimes listed as first “Patriarch” of Constantinople, though the episcopal see had not yet been elevated to that rank, Alexander served as bishop for about 23 years, until his death at 73 years of age, in 337. At the time of Metrophanes’ death, he left instructions in his will to elect his vicar to the throne of Constantinople.

During his episcopacy, Alexander engaged in debate with pagan philosophers and opposed heresies. He was highly praised by Gregory Nazianzus andEpiphanius of Cyprus.Theodoret called him an “apostolic” bishop.