According to the Liber Pontificalis, he was a Greek by birth. He restored the relations with the African and Eastern churches which had been broken off by his predecessor on the question of heretical baptism.
He is thought to be the author of the pseudo-Cyprianic writing Ad Novatianum, though this view has not found general acceptance. Another composition written at Rome, 253-258, is generally agreed to be his.
Shortly before the pontificate of SixtusII the Emperor Valerian issued his first edict of persecution, which made it binding upon the Christians to participate in the national cult of the pagan gods and forbade them to assemble in the cemeteries, threatening with exile or death whomsoever was found to disobey the order.
The remains of Sixtus were transferred by the Christians to the papal crypt in the neighbouring cemetery of St. Callistus.
For some time SixtusII was believed to be the author of the so-called "Sentences", or "Ring of Sixtus", originally written by a Pythagorean philosopher and in the second century revised by a Christian.
SixtusII was one of the first to fall a victim to this imperial enactment ("Xistum in cimiterio animadversum sciatis VIII.
The pathetic meeting between St. SixtusII and St. Lawrence, as the former was being led to execution, of which mention is made in the unauthentic "Acts of St. Lawrence" as well as by St. Ambrose (Officiorum, lib.
The feast of St. SixtusII and these six deacons is celebrated on 6 August, the day of their martyrdom.