The article presents a study on the organization of the World Anti-Imperialist Congress in Brussels in 1927, one of the results of which was the creation of an international organization - the League against Imperialism and Colonial Oppression. Drawing on materials from the league’s work in 1927-1937, stored in the funds of the Russian State Archive of Socio- Political History, the author reconstructs the progress of preparations for the congress. The circle of people who responded to the initiative to convene a world congress to discuss the problems of colonized peoples has been identified. The author revealed that the Comintern played a leading role in the preparation for this event, since the entire process of organizing the event, selecting delegates, as well as the agenda of the meetings completely depended on the directives of this organization. The reasons for disagreements that arose between the organizers of the world congress about the place and date of the event, as well as about the people who were supposed to be involved in the congress, were identified. The author concludes that the World Anti-Imperialist Congress in Brussels was a successful attempt to gather delegations from colonized regions around the world, which made it possible to actualize the problem of oppression of the Asian and African peoples. According to the author, the main result of the event was the creation of an international organization with an anti-imperialist orientation, which would become the forerunner of the decolonization process after World War II .