New Belgrade represented a material and social experiment for a new society in post-war Yugoslavia. As the city and the country were being simultaneously built, the philosophy of praxis was developing in both the Yugoslavian and the international scene. Praxis of Collective Building deals with the interactions between this school of thought and the histories of architectural construction sites. By closely studying the microhistories of construction, the author considers the theoretical problems of collective production through different narratives: voluntary youth actions in the construction of New Belgrade through the lens of Marxian praxis, participative prefabrication as a way of addressing housing shortages in Yugoslavia, and the transfer and adaptation of the Yugoslavian prefabricated system to the Cuban context by the microbrigade movement.