Alexander I succeeded Evaristus around AD 108 and governed the Roman Christian community for some seven years until his own martyrdom around AD 115. The Liber Pontificalis attributes to him the institutional decision of including the narrative of the Last Supper in the celebration of the Eucharist (the foundational moment of what became the Words of Institution in the Roman Canon) — though again the historical reliability of this 6th-century source for the early papal liturgical history is contested.
He was buried in the catacombs along the Via Nomentana (about seven miles outside the city walls) — the catacombs now called Sant'Alessandro, which were rediscovered and partly excavated in 1855 and which contain inscriptions from his cult continuous from the 4th century. The Roman tradition associates him with two other Roman martyrs (Eventius and Theodulus) traditionally martyred at the same location.