The chief source of information regarding Hilarion is the biography written by St. Jerome. The life of Hilarion was written by Jerome in 390 at Bethlehem. Its object was to further the ascetic life to which he was devoted. It contains, amidst much that is legendary, some statements which attach it to genuine history, and is in any case a record of the state of the human mind in the 4th century.
Hilarion was born in Thabatha, south of Gaza in Syria Palaestina of pagan parents. He successfully studied rhetoric with a Grammarian in Alexandria. It seems that he was converted to Christianity in Alexandria. After that, he shunned the pleasures of his day—theatre, circus and arena—and spent his time attending church. According to St. Jerome, he was a thin and delicate youth of fragile health.