Peter was the 18th Patriarch of Alexandria (301-313 a.d.) and is commemorated on the 29th of Hathor. Peter was the son of a priest. His mother made a vow during the Feast of Peter and Paul to call him after the Apostle. He suffered under Diocletian. There exists a Coptic homily on his life and martyrdom in addition to an encomium attributed to of Antioch narrating the life of Demetrius and Peter the patriarch.

The History of the Patriarchs provides a detailed account of his activities as well as his biography, in Syriac, Latin, Armenian, and Georgian. Under Peter the Seal of the Martyrs, Bishop Melitius of Lycopolis began a by going about ordaining clergy while Peter was in exile. The debate was over what measures could be taken to avoid persecution and how to deal with penitent who lapsed in order to avoid torture or death.

The texts attribute to him several works such as a homily on the Archangel Michael, a homily on baptism, extracts of a homily on Passion Week, in addition to several and fragments.