After becoming a Basilian monk, he opposed the Monothelite heresy which spread from Byzantium during the reigns of Heraclius (610-641) and Constans II (641-668), and for that reason moved to Brindisi with his disciples Gorgonius, Sebastius and Cyprius.
Relations between Rome and Byzantium worsened to the point that Pope Martin I excommunicated the Patriarch Sergius and the Monothelite heretics, but was arrested, deported to Constantinople and eventually exiled to Cherson in Crimea where he died in 655.
In Brindisi, the unyielding loyalty of Pelinus in the circle around the bishop Proculus likewise brought him to breaking point in his relations with the court of Constantinople.
On this occasion a "Life" was composed, quite possibly also by the agency of Cyprius in order to promote Brindisi as the centre of the cult of his predecessor.
The former Corfinio Cathedral, now a basilica, is dedicated to him, and his cult in the Marsica area is attested by the name of the small town of San Pelino, a frazione of Avezzano, where he is said to have passed by on his return from a journey to Rome.