St Peter, chief of the Apostles, is shown bust-length against a dark background. He is gazing upwards, with his hands clasped in prayer before him. St Peter's repentance, following his denial that he knew Christ (Mark 14.72), became a popular subject in painting from the time of the Counter-Reformation. This painting resembles the general type of St Peter penitent, though the saint is more typically pictured by Reni as balding.

Numerous pictures of the subject by or associated with Reni are recorded from the seventeenth century onwards; this work is perhaps closest to the studio variants of the 'St Peter Penitent' in the Galleria Doria Pamphili, Rome.