John, bishop of Jerusalem (387-417), was directly involved in two Palestinian synods of 415, whose aim was to judge Pelagius’ orthodoxy. The synod held in Jerusalem was summoned by John himself, who was also among the fourteen bishops who declared Pelagius orthodox in the following synod of Diospolis. However, his theological understanding of Pelagius’ position is difficult to evaluate because almost all his literary production has not came down to us. However, at least one of his work written during the Pelagian controversy has survived: it is his Profession of Faith (CPG 3621). Unfortunately, modern scholars have paid little attention to this text, mainly due to his difficult textual tradition: only the Syriac and the Armenian version is edited, while the Greek version, though present in only one manuscript, has not yet been published. Basing our study on the Greek version, we will analyse John’s Profession of Faith to clarify his knowledge of the theological questions involved in the controversy between Jerome and Pelagius, and his position in this controversy. It will be shown that John was well aware of what Pelagius thought in those year, and, that, at least partially, he agreed with Pelagius. This study will contribute to a better understanding of how deep was the penetration of the Pelagian doctrines among Eastern Christianity.