The only sources on Petronius are a letter written by Bishop Eucherius of Lyon (died 450–455) to Valerianus, and Gennadius' De viris illustribus.

Gennadius writes that Petronius belonged to a noble family whose members occupied high positions at the imperial Court at Milan and in the provincial administrations at the end of the fourth and the beginning of the fifth centuries.

[2] About 432 he was elected and consecrated Bishop of Bologna, where he erected a church to Saint Stephen (Santo Stefano), the building scheme of which was in imitation of the shrines on Golgotha and over the Holy Sepulchre in Jerusalem.

Germain Morin published a sermon entitled "In die ordinationis vel Natale episcopi" (Revue bénédictine, 1897, 3 sq.

Shortly afterwards a church was erected in his honour at Bologna; a second, San Petronio Basilica, planned on a large seal, was begun in 1390.