Relevance. The relevance of identifying methodological problems in the study of bilingualism and its impact on individual and social processes is due to the economic, political and socio-psychological characteristics of modern multicultural and multilingual societies. The special significance of the study of bilingualism acquire in the Russian language context. It is characterized by the need to find a balance between raising the status of the Russian language (as the main unifying factor of civil identity) and the development and preservation of the languages of the peoples of Russia (as an important component of the ethnocultural identity of their representatives).

Objective. The work is aimed at the analysis of the main methodological problems that arise during the research of bilingualism, identifying its impact on cognitive processes and the relationship of bilingualism with ethnocultural identity.

Method. From the point of view of the system approach and cultural-historical psychology, a critical analysis of studies of bilingualism, its impact on cognitive processes and the relationship with ethno-cultural identity was carried out.

Results and conclusions. Methodological problems that complicate the study of bilingualism, systematization and generalization of their results, and the application of the results in various spheres of social practice are identified. A number of methodological challenges need to be overcome in the field of studying the impact of bilingualism and multilingualism in order to obtain valid and reliable research results and implement practical, socially significant tasks in the field of preserving the languages of the peoples of Russia along with strengthening the status of the Russian language. The need for interdisciplinary studies of bilingualism and its impact on cognitive processes and ethnocultural identity based on the application of a systematic approach, including in the Russian multilingual context, is shown.