He was a pupil of Isaac, the catholicos-patriarch Isaac the Great of Armenia or Isaac of Seleucia, and of Saint Mesrop. At their request he went first to Edessa, then to Constantinople to perfect himself in the various sciences and to collect or copy Syriac and Greek manuscripts of the Bible, and the writings of the Fathers of the Church. He returned to Armenia after the First Council of Ephesus (431).
In addition to his labours in connection with the new version of the Bible and various translations, he composed several works, the principal of which is his remarkable treatise "Against the Sects" or "On God". It was written between 441 and 449, and contains four books or chapters.
In the work Eznik displays much acumen and an extensive erudition. He was evidently as familiar with the Persian language (Middle Persian) as with Greek literature. His Armenian diction is of the choicest classical type, although the nature of his subject matter forced him to use quite a number of Greek words.