The end of the First World War in Iran was marked by the emergence of a new political order that aimed at diminishing provincial and tribal autonomy throughout the country and achieving a single economic market. Reza Khan/Reza Shah’s policy of centralizing government power and implementing reform in interwar Iran (1921-1941) accelerated the process of urbanization and consequently enhanced the degree of interdependencies between the provinces. The development of new industries that had been under way since the late nineteenth century increased the numbers of the urban working class such that by the early 1920s they were agitating for better working conditions. Organized and non-organized labourers engaged in mass activities such as strikes, sit-ins and demonstrations. Obviously, the neighbouring Soviet Union and the Communist International – the Comintern – could not remain indifferent towards such labour activism in Iran. Therefore, the communist movement in Iran was largely intertwined with the country’s labour activism. By utilizing the history of the Comintern, the miscellaneous Soviet Moscow and Baku archives, and personal narratives of Iranian labour and communist activists, the present study intends to examine the Soviet/Comintern stance towards social and political developments in Iran, and whether the habitually accepted periodization of the history of the Comintern is applicable to the history of Iranian labour activism and the communist movement during the Iranian interbellum.