The article examines the Soviet Union’s policy in Afghanistan during the period of its military presence there (1979–1989) as a set of measures corresponding to the modern interpretation of the concepts of nation-building and state-building. It also analyzes modern theories of nation- and state-building and highlights their main trends, forms, and problems. The author also proposes a unique approach that combines these two concepts as “nation-state-building” in relation to the Soviet project in Afghanistan. The article elaborates on the main tasks of the Soviet policy in the 1980s in Afghanistan as well as their implementation and results. Due to the combination of “nation-building” and “state-building” concepts in a complex structure of “nation-state-building”, the article draws conclusions, first, about the applicability of this approach to the specific Soviet project of state-building in Afghanistan, and, second, about the complexity of the project itself, which included ideological, political, economic, and military components. On the basis of archive documents, memoirs of military and diplomatic actors, and a wide scope of academic research, the author substantiates the idea of large-scale tasks of nation-state-building in Afghanistan in Soviet foreign policy, and also indicates that the implementation of the project encountered great difficulties from the unfolding civil war to the inability of the Afghan leaders to consolidate the political life of the country. Soviet leadership quickly realized the unreadiness of the Afghan society for the proposed systemic social transformations. Despite the fact that the goals of the Soviet project were not achieved, this does not diminish its scale and historical significance.