He is known as the outstanding father of the monks in Ireland. He was founder and first abbot of Bangor Abbey on the south side of Belfast Lough. He was a pupil and close friend of St.Columba who took Irish monasticism to Scotland.

He started a monastery on Lough Erne. He was known for his extreme austerity. He founded a monastery as well in Bangor on a site well placed for sea travel to both Scotland and Gaul. It was said to have three or four thousand monks but this may refer to the number who passed through it during the time Comgall was abbot. There is a monastic rule attributed to him which survives in Irish. The rule can be summed up in three ways: (1) patience (2) humility and (3) the love of the Lord in your heart.