The article examines the theoretical foundations of the international legal nature of multilateral development banks. The methodological basis of the study was a complex systematic analysis of legal phenomena, as well as private scientific methods of knowledge: formal-legal, historicallegal, and comparative-legal. It indicated that multilateral development banks are international organizations that meet all the characteristics of subjects of international law – they have their own will, competence, and responsibility. Multilateral development banks are international organizations of a special type that combine public and private foundations in terms of competence. It noted that multilateral development banks create conditions for cooperation between states in matters of financing the economy. Development banks created as international organizations based on multilateral agreements for joint management of international settlements in the field of financial cooperation. Multilateral development banks as subjects of international law are capable of responding quickly to changes in the world economy. The purpose, tasks, functional features of multilateral development banks constantly being transformed, which corresponds to modern trends in the development of international legal and economic relations. It indicated that multilateral development banks, as international intergovernmental organizations, have their own legal personality and do not fall under the jurisdiction of the national states on whose territory the headquarters are located. Development banks have international immunities and privileges that are functional in nature. A feature of the legal status of multilateral development banks, as subjects of international public law, is the combination of public and private functions due to the private law and public-law nature of their activities. This manifested in the fact that the financial operations of international multilateral development banks are similar to market financial operations, but credit agreements are international contracts concluded with states. A special aspect of the legal activity of development banks is the influence on social and economic reforms in member states by financing development programs.