This study presents details on many religious elements of both Aztec and Spanish practices in the 15th Century before their contact and then in the first century of Spanish culture in New Spain. There are already excellent studies of 16th-century Spanish Catholicism and of the religion of the Aztecs. Histories of Catholic missions have mapped the processes of evangelization in New Spain with each of these fields of investigation committed to methodologies of its guild. Yet these studies also end up presupposing an “insider” and “outsider.” We undertake an investigation that attempts to give each “side” an equal voice.