This article analyses the evolution of language policy in the former Soviet Union with reference to documentary sources and its relationship with national policy and the Constitution. The rapid changes in the national policy of the USSR, starting with the idea of full equality of all nations and the right to self-determination, with subsequent changes towards the rapprochement of peoples, influenced the language policy, which evolved from multilingualism to bilingualism with an emphasis on the Russian language. It is important to note that the Russian language did not have a clear legal status in the USSR Constitution, unlike the national languages, which were enshrined in the constitutions and language laws of the Soviet republics. The Russian language mainly spread through administrative decrees, which led to negative consequences such as manipulation of language issues by local nationalists and the emergence of national conflicts, and influenced the process of the collapse of the Soviet Union. Compared to the modern European Union, where English dominates over other languages, the USSR represented a different version of language coexistence and a different language policy. This emphasizes the importance of finding a balance between the unity and diversity of languages and cultures of nations. The lack of a clear position on multilingualism and manipulation of the national sense of language as an indicator of identity contributed to tensions and aroused all kinds of emotions, thus provoking conflicts on cultural and national grounds.