Saint Dalmatus had served in the army of the holy emperor Theodosius the Great (379-395) and gained his notice. He left the world somewhere between the years 381-383, and went with his son Faustus to the monastery of St Isaac near Constantinople. St Isaac (May 30) tonsured father and son into monasticism, and they both began to lead a strict ascetic life.

Once during Great Lent St Dalmatus did not eat any food for the forty days. Later he regained his strength and was found worthy of a divine vision.

When St Isaac was approaching the end of his earthly life, he named St Dalmatus as igumen of the monastery, which later became known as the Dalmatian Monastery.

St Dalmatus showed himself a zealous proponent of the Orthodox Faith at the Third Ecumenical Council at Ephesus (431), which condemned the heresy of Nestorius.

After the Council the holy Fathers elevated St Dalmatus as archimandrite of the Dalmatian monastery, where he died at the age of ninety (after 446).

St Faustus, like his father, was a great ascetic and particularly excelled at fasting. After the death of his father, Faustus became igumen of the monastery.