[2] Older sources use the spelling Xystus (from the Greek ξυστός, xystos, "shaved") in reference to the first three popes of that name.

According to the Liberian Catalogue of popes, he served the Church during the reign of Hadrian "from the consulate of Niger and Apronianus until that of Verus III and Ambibulus", that is, from 117 to 126.

Eusebius himself begins to show internal inconsitencies for the chronology of this period; Richard Adelbert Lipsius compares the available sources and asserts that Sixtus died between around 125, after a tenure of 10 years.

[5] Like most of his predecessors, Sixtus I was believed to have been buried near Peter's grave on Vatican Hill, although there are differing traditions concerning where his body lies today.

In Alife, there is a Romanesque crypt, which houses the relics of Pope Sixtus I, brought there by Rainulf III.