Sixtus was born a Greek but nothing else is known about his early life. He appears to have been an adult convert to Christianity. He then became a deacon in Rome and, on August 30, 257, was elected Pope amidst the persecutions of Valerian.
As Pope, Sixtus upheld Pope St. Stephen's teaching that baptism by heretics was legitimate. However, where Pope St. Stephen had threatened to excommunicate the bishops who refused to adhere to this doctrine, Sixtus did not break off relations with these bishops, instead trying to communicate with them.
Mass was often celebrated in the catacombs, literally underground, to avoid capture by the authorities during the persecutions. The Cemetery of Calixtus was most frequently used, however, by the time of Pope Sixtus' reign, this place had become known to the authorities. Therefore, Sixtus relocated the celebration of Mass to the Cemetery of Praetextatus. However, despite these precautions, the authorities located the Pope and, in early August 258, arrested the Pope and his deacons at the cemetery while they were celebrating Mass. They were taken to the prefect for a formal judgment.
St. Lawrence, the chief deacon, had not been present during the arrest and, upon hearing the news, rushed to Sixtus' side, desiring to die with him. He said to the Pope, "Where are you going, father, without your son? Where are you going, O priest, without your deacon?" Sixtus replied, "My son, you I am not abandoning. Greater strife awaits you. Stop weeping; you will follow me in three days."
On August 6, Pope Sixtus was brought back to the Cemetery of Praetextatus where he was beheaded. He was buried in the Cemetery of Calixtus. He had been Pope for less than a year.
Pope St. Sixtus II is the patron saint of Bellegra, Italy.