He was born of a Christian family in Damascus in the second half of the seventh century, where his father was a high official under the Umayyad caliph; a post which he inherited. When the Iconoclast movement (seeking to prohibit the veneration of icons) gained acceptance in the Byzantine court, John, being under Muslim rather than Byzantine rule, was able to write effective treatises attacking Iconoclasm and attacking the emperor for supporting it. At about this time he retired to the monastery of Saint Sabas near Jerusalem, where he became a monk and was ordained. He died in the middle of the eighth century.
He wrote many theological treatises in a dangerously clear and accessible style which made the issues understandable even by non-experts. His name was reviled and execrated by the imperial Iconoclast party even after his death. Sometimes known as "the last of the Church Fathers," he was declared a Doctor of the Church by Pope Leo XIII in 1883.