Millions of devotees acclaim the Nahuatl-language Nican mopohua account of the apparitions of Our Lady of Guadalupe to Juan Diego as the foundational text of the Guadalupe tradition. A number of scholarly analyses have also examined the Nican mopohua as a prime source for that tradition. But no previous study has focused on a theological examination of Luis Laso de la Vega's Huei tlamahuiçoltica (1649), in which the Nican mopohua was first published. Huei tlamahuiçoltica is the premier Guadalupan pastoral manual and encompasses other important material, such as the Nican motecpana account of miracles attributed to Guadalupe's intercession, and the earliest published synopsis of Juan Diego's life posed as a model for Christian discipleship. This article explores Laso de la Vega's contributions and the ongoing significance of his treatise for the development of theological works and pastoral ministries centered on Guadalupe.