In accordance with his hardly paralleled mastering of virtually all the religious and literary traditions of the ancient Near and Middle East, in particular ancient Iran, which let his academic expertise encompass an area extending from Asia Minor to Iran and Central Asia, throughout a millennium, Geo Widengren showed some interest for Mani and Manichaeism as well. Although less known than his studies on older Iranian religious traditions, his research on Manichaeism is nonetheless worth being discussed. In Widengren’s perspective, if we consider the area in which the Manichaean tradition originated, before its universalistic spreading towards East and West, this religion might be, in fact, perceived as one of the last outcomes of Persian tradition. It is just as such that Widengren investigated it, videlicet assuming a pan-Iranian model of historical diffusion. The present chapter provide a reconsideration of Widengren’s contribution in the light of recent scholarship on Manichaeism.