The article deals with the problems of studying folk hagiography, a complex of peasants’ written and oral texts, which contain information about saints or revered non-canonized devotees and express the very specifics of the popular understanding of holiness. The first half of the article discusses the phenomenon of folk hagiography, defines the range of folklore genres, reflecting folk beliefs about saints, and investigates the mechanisms of interaction between the written and oral traditions. The second half analyzes texts and religious practices related to the folk worship of the non-canonized elder Judas Koneschelsky (Archangelsk North). There are following sources for the study of this cult: judicial documents of the turn of the 19th and the 20th centuries, a peasant’s diary of the turn of the 19th and the 20th centuries, local priests’ notes from that time, and field data, collected by folklorists at the beginning of the 21th century. On the basis of these sources, the authors, considering a specific case, make an attempt to study the mechanisms of functioning of folk hagiography. A large time span between the early and late data records and various texts about Judas make it possible to trace evolution of this cult.