The article substantiates the strengthening of cities in global processes. The practice of creating twin cities has emerged as a means of promoting international cooperation at the subnational level. Twin cities share cultural, economic, technological, and other experiences, and behave much like brothers and sisters. The most influential of them – global cities-are becoming increasingly important for political issues, as they organize and use various international networks built outside the official framework. Based on urban diplomacy and paradiplomacy, twin cities enter into mutually beneficial relations with many actors of the world system, achieving the realization of their interests and further strengthening national influence. Special attention is paid to Saint Petersburg, which combines the role of a global city with the functions of a sister city. The conclusion is made about the successful international strategy of Saint Petersburg and the features of the twinning model.