Studying the history of ethno-cultural interactions in a multiethnic society is of scientific and practical interest.
 
 The purpose of the study is to examine the historical conditions and factors of the penetration and spread of Catholics and Protestants in the Kazan governorate in the XVIII–XIX centuries, to analyze the features of social and intercultural communications.
 
 Materials and methods. The article is based on the analysis of literary and documentary materials. The main sources of research were archival documents, legal acts, materials of censuses, periodicals. Theoretical generalizations and conclusions are made using the chronological, typological methods, institutional and cultural-anthropological approaches.
 
 Study results. Catholics and Protestants penetrated the Kazan governorate in the XVIII–XIX centuries from the countries of Western Europe. The historical conditions of their resettlement were the development of the Russian Empire, the development of new territories, the need for qualified personnel in various spheres of state and public activity. The reasons for the relocation were due to wars, social movements, as well as voluntary departure of foreigners to the Russian regions for the purpose of employment, temporary or permanent residence. Catholics, represented mainly by Poles, more often adhered to religious traditions, while Protestants, due to greater simplicity of their cult, less ritualism, simplified apologetics, more actively interacted with the Orthodox population, exerting a certain influence on it. Western Christians had a high social status, were employed in government, military service, in the fields of science and education, healthcare, trade, etc. Despite their relative small number, Catholics and Protestants have left a noticeable mark on the history and culture of the multi-ethnic region. The interaction between the Russian Orthodox Church and other traditional confessions with Catholicism and Protestantism was carried out on the basis of Russian legislation, which regulated their religious and social activities, prohibited missionary work among Russian subjects.
 
 Conclusions. During the period under review, the religious diversity of Kazan governorate was supplemented by Western Christian confessions and denominations, making it even more mosaic. Resettlement of Catholics and Protestants was caused by political, economic, socio-cultural reasons. The dynamics of the quantitative and qualitative composition of Western Christians depended on the historical conditions in Europe and Russia. Tsarism supported resettlement of foreigners, created the legal basis for their residence and professional activity, respected freedom of religion, but forbade converting Russian citizens into their faith. The results of the study make a definite contribution to the study of ethno–confessional processes in Kazan governorate in the XVIII-XIX centuries, enabling to better understand the nature of modern ethno-cultural communications in polyethnic regions of Russia.