The article charts and discuss the historical use of the concept of imperialism in the Communist International(Comintern; Third International, 1919–43). By analyzing first, the establishment and framework of theComintern’s understanding and use of imperialism as a political and instrumental tool, the aim of the articleis to look beyond the official and sanctioned policy of the Comintern on imperialism between the wars. Indoing so, the author examines and discuss internal discussions as they evolved over time at Cominternheadquarters in Moscow by analyzing documents filed in the Comintern Archive (RGASPI) in Moscow. Keyconcepts focus on the Leninist perception of imperialism; the periodization debate, and contextualexplanations linked to the frequent policy shifts of the Comintern and its relation to Bolshevization andStalinization. In conclusion, the article highlights the historical trajectory of imperialism and anti-imperialism as a constituent source of Bolshevik policy making in its interpretation of global society.