This article insists on the importance of a very complex and intriguing Byzantine Greek text, usually deno­mina­ted Narratio de rebus Persicis, De Gestis in Perside, or Dispu­ta­tio de Chri­sto in Persia, which contains a large amount of extremely interesting material enabling a better comprehension of the image of Iran in Western Late An­ti­qui­ty from the point of view of the contemporary Christian perception. Among the main aims of this book, full of compo­si­tional strata of different origins and times (e.g. the very important and ar­chaic prophesy of Jesus’ birth through the voice of a star appeared to Cyrus the Great in a temple), one was certainly to criticise the ex­tre­mely polemical att­i­tude of opposing Chris­tian Churches and communities in the East, particularly in the milieu of the Sasanian Empire. In fact, the great framework of the present work is occasionally offered by a theological debate, lasting for days, which should have been taken at the court of a fictitious Persian king, named Ἀρρινάτος. This study offers new arguments sup­porting the presence in such a frequently forgotten Greek source of some clear re­fe­ren­­ces to the kingdoms of Kawād I and Xusraw I, with particular reference to an­ti-Mazdakite polemics. Fur­thermore, the fi­nal part of the article proposes an Iranological evaluation of the resonance produced by the na­me of the Persian pro­ta­go­nist of the whole book, the wise Aphro­di­tianus (Ἀφροδιτια­νός).