Introduction. The article examines peculiarities of missionary activities performed by the Russian Orthodox Church among Buddhists of Eastern Siberia in the mid-to-late 19th century. Goals. The paper aims to analyze — in social and archaeographic perspectives — a Tibetan manuscript collection at the Institute for Mongolian, Buddhist and Tibetan Studies (SB RAS) compiled through efforts of the Orthodox Christian missionary Konstantin K. Stukov (1809–1883). Materials and methods. The so called ‘cognitive history’ and certain elements of historical phenomenology serve as a methodological basis of the research. The structure of the Stukov Collection contributes to further understanding of both functioning patterns inherent to mid-to-late 19th century Buddhist communities of Eastern Siberia — and essentials of concurrent Orthodox Christian missionary endeavors across the region. The main research problem is to determine the substantial specifics of this collection for subsequent reconstruction of certain aspects in missionary activities of the priest. Conclusions. Ven. Stukov was interested in exploring worldviews and ritual practices of lay Buddhists for the cause of his missionary work. Those to be learnt knowledge areas (besides fundamental Buddhist doctrines proper) were to include visions of life characteristic of native inhabitants and largely rooted in pre-Buddhist culture of Siberia, South and Inner Asia. And the paper suggests that very interest proved crucial to the success of Ven. Stukov’s missionary deeds. The analysis claims personal initiative was an important factor of missionary work in mid-to-late 19th century Eastern Siberia integral to the then (and there) government policies at large. The article also introduces some newly discovered episodes from the biography of Konstantin K. Stukov — an Orthodox Christian priest, ethnographer, and social activist.