The present article aims to shed light on the professional activities of the historian and mathematician Sharaf al-Dīn ‘Alī Yazdī and his afar-nāmah. In so doing, two questions are addressed: (1) Did Yazdī’s expertise in mathematics influence his historical narrative? (2) Did Yazdī simply expand on Niām al-Dīn Shāmī's afar-nāmah, composed some twenty years earlier? Comparing the frequency of quantitative and qualitative data in Yazdī's and Shāmī's afar-nāmahs, the article finds that although Yazdī made an effort to incorporate quantitative data in his history, his narrative is not particularly informed by his expertise in arithmetic. This seems, at first glance, a byproduct of a predominant tradition in the Islamic-Iranian historiography, which makes extensive use of literary techniques. The comparison between the two afar-nāmahs, however, suggests that both Yazdī and Shāmī subscribed to a notion of “accuracy” which bore little resemblance to its modern counterpart manifested in quantitative precision. Finally, the article concludes that the allegation of plagiarism against Yazdī is unfounded.