The paper deals with a rather rare and little-studied text – the “Chronicle” of John of Nikiu, a Coptic chronicler who lived in Egypt in the second half of the 7th century and headed the bishopric in the city of Nikiu. The “Chroni-cle”, preserved only in Ethiopic version, contains many valuable testimonies on Egypt during the Arab conquest (640–643). The author examines the sources of John of Nikiu, trying to answer from whom John borrowed his evidence on the Moors who served in army of Byzantine Emperor Heraclius (610–641). Based on this subject, the author is looking over a historiography tradition that John followed when describing the way of life and tribal organization of the Moors who lived west of the Nile Delta. Having compared the evidence of John of Nikiu and John of An-tioch, a unique Greek-speaking author living in the 7th century and mentioned the presence of the Moors within He-raclius’ army, the author concludes that John of Nikiu used the testimonies of the prominent Byzantine 6th-century historian Procopius of Caesarea, an eyewitness to the reign of Emperor Justinian I (527–565). John of Nikiu read Procopius’ works, as he himself strictly says, and, respectively, thanks to Procopius, John knew well about the tribal behaviour and political structures of the Moors. According to the author, Procopius influenced John not only in sub-jects, but also in emotions: like Procopius, John of Nikiu declared a sharp negative assessment of the Moors’ behaviour and tribal life. The Coptic chronicler constantly labeled them as barbarians.