According to Bede, he was a Berber native of North Africa, and abbot of a monastery near Naples, called Monasterium Niridanum (perhaps a mistake for Nisidanum, as being situated on the island of Nisida). He was twice offered the vacant archbishopric of Canterbury, by Pope Vitalian, but modestly declined the appointment. He first recommended that it should be given to Andrew, a monk belonging to a neighbouring monastery(monachum quemdam de vicino virginum monasterio), who also declined on the plea of advanced years. Then, when the offer was again made to Adrian, he introduced to the pontiff his friend Theodore of Tarsus, who then chanced to be at Rome, and who consented to undertake the charge. Vitalian, however, stipulated that Adrian should accompany the new archbishop to Britain. He gave as his reasons that Adrian, having twice before made a journey into Gaul, knew the road and the mode of travelling.
The two set out from Rome on 27 May 668, and proceeding by sea to Marseille, crossed the country to Arles, where they remained with John, the archbishop, till they got passports from Ebroin, who ruled that part of Gaul as Mayor of the Palace, for the minor king Clotaire III. Having then made their way together to the north of France, they parted company, and went severally to reside for the winter, Theodore with Agelberctus, bishop of Paris, Adrian first with Emmon, bishop of Sens, and afterwards with Faro, bishop of Meaux. Theodore, being sent for in the following spring by King Ecgberht of Kent, was allowed to take his departure, and he reached England at the end of May 669; but Adrian was detained by order of Ebroin, who is said to have suspected him of being an emissary of the Greek emperor sent to stir up troubles against the kingdom of the Franks. At length, however, the tyrant became convinced that there was no ground for this notion, and Adrian was permitted to proceed to England, where, immediately on his arrival, he was made abbot of the monastery of St. Peter (afterwards called St. Augustine's Abbey) at Canterbury, an appointment which was in conformity with instructions given by the pope to Theodore. Such is the account given in the Ecclesiastical History (iv. 1.). Adrian was known to be a man learned in the Bible, as well as in Greek and Latin, and an excellent administrator. Under his direction the abbey came to have substantial, far-reaching influence.