A state level integration process should first and foremost have a positive impact on the border areas. The current Russian-Belarusian and Russian-Kazakhstan borders acquired the status of ‘state borders’ in 1991 as a result of the collapse of the Soviet Union. While Russia and Belarus immediately embarked on the path of integration in the 1990s, effectively cancelling border controls, Russia and Kazakhstan were forced to resolve border security issues by strengthening their border and establishing customs control processes. The launch of the Customs Union in 2010 partially removed the existing trade contradictions, and the creation of the Eurasian Economic Union (EAEU) in 2015 significantly strengthened interstate interactions. However, despite the de-clared integration, it could not compensate for the dividing role of the border which separates the diverging political, legal, and economic spaces of the three countries. The purpose of this study is to determine whether divergence or convergence occurs in the considered border regions, as seen through the prism of demographic, ethno-cultural and economic changes. We rely on the results of a multi-year field research in various regions of the Russian-Belarusian and Russian-Kazakhstan borderland (2014–2018), data from official statistics, and some conclusions based on the authors’ findings as part of their work on previous collective research projects. We found out that demographic processes became one of the reasons, as well as the main driver of divergence. The active depopulation evidently decreased the potential for cross-border cooperation (especially at the local level). The Russian-Belarusian borderland is still rather homogeneous in sociocultural sense, and the border between Russia and Kazakhstan is characterized by an increase in ethno-cultural divergence. The post-Soviet period of nation-building in Kazakhstan was a period of the revival of the national language and kazakhization of the public space. Our analysis demonstrates the crucial importance of path dependence in the economic cooperation on the whole and in the specialization of interregional interactions. We observed both autonomization and absence of cross-border cohesion in the economic sphere, and in many cases, we saw examples of competition.