Interregional and cross-border cooperation of libraries are performing an important humanitarian mission. The relevance of the study is determined by the great importance that the Russian Federation attaches to the development of cultural ties between regions and border territories within the Commonwealth of Independent States. The purpose of the article is to reflect the results of the study conducted by the Russian State Library on cooperation of central universal libraries of the CIS member states in the professional sphere. The author has performed the analysis of current regulatory interregional and cross-border cooperation legal acts and documentation of the CIS member states, the partnerships of central universal libraries of border regions of the Commonwealth countries and the experience of their scientific and methodological activities. She has studied the promotion of information on interaction with colleagues from neighboring countries in the media and Internet. Factors influencing cross-border cooperation of libraries of the CIS countries are determined. Positive factors include: availability of an up-to-date regulatory framework for cooperation; availability of a space for common language communication; participation of public organizations, the population, ethnocultural societies in contacts with foreign colleagues; support of local media in promoting information about cooperation. Factors that have a negative impact on cooperation are as follows: border claims of states and changes in geopolitics; presence of language barriers; weak material and technical and information and communication infrastructure. The practical result of the study is the development of the “Concept for the Development of Library and Information Space Based on Border Libraries of the CIS Member States” and an action plan for its implementation until 2030.