Justus wrote, according to Photius (Bibl. cod. 33), a chronicle of the Jewish kings, from the time of Moses down to the death of Herod, in the third year of the reign of Trajan. The style of the work, which is lost, is said by Photius to have been concise, and the author omitted many of the most important events, such as the history of Christ, which it was a common practice with Jewish writers to pass over unnoticed.

Justus is further charged with having falsified the history of the wars with Rome, which led to the destruction of Jerusalem. (Comp. Joseph. Vit. §§ 37, 65, 74, who gives a long account of him, and censures him very severely.) He edited his work after the death of Agrippa and the other great men of the time, because, as Josephus says, he knew that his accounts were false, and had reason to fear the consequences. Some writers (Euseb. Hist. Eccl. 3.9; Steph. Byz. s. v. Τιβερίας) speak of a work of his on the Jewish war, but this may refer only to the last portion of his chronicle, which Diogenes Laertius (2.41) calls a Ζτίμμα

Suidas (s. v. Ἰοῦστος) mentions some other works of Justus, of which however not a trace has come down to us.