After providing a general introduction on how Greco-Roman sources treated the figure of Zarathushtra, the prophet and founder of the Persian religion, who was considered both as a sorcerer and as a sage, this paper investigates two less known passages dealing with different interpretations of Zarathushtra. Arnobius and the author of the Pseudo-Clementines emphasise his role as a magician and attest to some implied links with Gnostic literature and doctrines, also by means of some connections with Biblical figures.