Caesarius entered the monastery of Lérins as a young man, was sent to Arles to recover his health, and was ordained priest. In 502 he was elected bishop of Arles, a see which under his forty-year governance became the metropolitan see of southern Gaul.
He was the great preacher of Latin Gaul. His 238 surviving sermons — preserved in greater number than any pre-Carolingian Latin author — show him explaining the Scripture and Christian doctrine to ordinary congregations in simple, vivid Latin; many were preached to be read aloud by other priests in their own parishes, an early model of the homiletic resource.
He presided over a series of councils, most famously the Council of Orange in 529, which condemned semi-Pelagianism and affirmed Augustinian grace — closing a hundred-year debate decisively for the Augustinian tradition. He founded the monastery of Saint-Jean for women at Arles, with his own sister Caesaria as its abbess; the Rule he wrote for it is the first extant monastic rule for women.