Three executioners fighting to straighten the cross. Peter is already nailed to the rafters, his hands and feet are bleeding. The apostle is practically naked, which emphasizes his vulnerability. He is an old man, with a gray beard and a bald head, but his aging body is still muscular, suggesting considerable strength. He rises from the cross with great effort, turning his whole body, as if he wants to look towards something that is out of the picture (God). His eyes do not look at the executioners but he has a forlorn look.

The most striking feature of the painting is its pronounced realism: the saint is a poor fisherman from Bethsaida, and the executioners, their hands heavily veined and reddened, their feet dusty, are toiling workmen. This was the beginning of a new phase in Caravaggio's art where he concentrated on the Christian ethos of humility and salvation through suffering.