In our time many developed countries receive significant migration flows, but there is no political and public consensus about their positive impact on the economy of host countries. The particular disagreements concern the social policy, the problems of budgetary funds for the integration programs, benefits for immigrants, and the impact of immigration on the future of the economies of developed countries. The aim of the study is to identify the impact of migration of human capital on the sustainability of the socio-economic system More specifically, the papers looks at the following issues: the impact of international labour migration on the sustainability of developed economies; the most significant (on this topic) characteristics of the human capital of migrants, the impact of migration on host and donor countries, the impact of migration on social protection systems, a set of characteristics of both migration and the host country to assess the likely effects of migration (on the example of EU countries). The methodology of the research is based both on the review of scientific literature and on the theoretical analysis of economic theory in order to provide arguments for the economic benefits of human capital migration for both recipient and donors countries, and to systematize the benefits and costs of migration of human capital. Theoretical analysis showed that, on the one hand, the influx of migrants creates a burden on social protection systems, on the other hand, developed countries taking the main migration, need of labour force and must compete for human capital of high quality. Although the integration of refugees entails large preliminary short- and medium-term financial costs, if successful, it will bring financial benefits in the long term. It is shown that the migration of human capital leads to the formation of a diversity of labor resources as a factor of sustainability of the socioeconomic system. The findings and results of the study can be used for theoretical research and forecasting of social and economic change. Governmental organizations can use the results to improve the efficiency of social and migration programs.