This preliminary paper attempts to think about the question of polycentric leftist internationalisms after the collapse of the centralized Third International in the intersected periods of early Cold War and tricontinental decolonization (1950s-1960s). It does so through an investigation of selected Indonesian political actants, particularly ones that were affiliated with the Indonesian Communist Party, whose praxes were guided by variations of Marxist materialist analysis and their revolutionary itineraries of collective self-determination, the struggle against dominating power by the subaltern masses, and the flourishing of society as a whole. This paper suggests that there are at least three competing, yet overlapping, leftist internationalist assemblages in this period aiming to form a global alliance against different forms of persisting and emerging imperialisms: Soviet, Bandung, and Maoist internationalisms. Soviet internationalism created several polarized “fronts” to link different communist bodies based on social issues, namely, democratic youth, student union, trade union, women, and peace, in which youths (Pemuda Rakjat), laborers (SOBSI), and women (Gerwani) were actively involved. Bandung internationalism provided platforms for newly independent African and Asian nations to remake global relationality and perform different types of transcontinental exchange among students, journalists, women, Muslims, filmmakers, writers, lawyers, economists, and laborers, drawing in an ideologically diverse range of activists, from cultural workers in Lekra, to LKN and Lesbumi. Lastly, Maoist internationalism offered a militant anti-revisionist alternative to Soviet internationalism in addition to its emphasis on anti-imperialism and anti-racism, radicalizing the actions of peasants (BTI), Chinese (Baperki), and the People’s Guerrilla Forces in North Kalimantan.