In due time, he was instructed in Sacred Theology and became a deacon. In 424, the Bishop of Ravenna died, and Cornelius of Imola, who was seen as the most qualified successor, went to Rome with his deacon Peter to obtain the papal confirmation.

St. Sixtus III, who was inspired by a vision of St. Apollinaris, the first Bishop of Ravenna, refused to ratify the election and appointed Peter in his place. Peter was nicknamed Chrysologus, which means Golden-speaker, on account of his exceptional eloquence.

All his sermons were very simple and short, for he was afraid of fatiguing the attention of his hearers.

He died in 450 and was later declared Doctor of the Church.