Iranians actively took part in the Vietnam War on the both sides. Under Shah, Iran even sent pilots and ground forces to fight in Vietnam. On the other side of the war, the Iranian revolutionary opposition staunchly backed the North Vietnamese side and often justified its position as part of support for decolonization. In the decade leading to the Iranian revolution of 1979, Vietnam was one of the main topics of intellectual engagement and political propaganda. How to make sense of the Iranian contributions to a conflict so far away? Iranians’ approach to the Vietnam War clearly made sense as part of the Cold War. Shah’s staunch anti-communism meant that its backing of the US in the Cold War wasn’t just based on geopolitical concerns but had a serious ideological component. At the same time, Shah’s intervention in the conflict wasn’t straightforwardly pro-American and had elements of autonomy. The Iranian state-controlled press didn’t took up the cause of the South Vietnam and its coverage sometimes verged on being anti-war. Iran’s own military contribution to the war was kept hidden and Iran was much more enthusiastic in offering help to international mediation efforts. Tehran also criticized the US conduct of the war and attempted different channels to help bring it to an end: this included Shah’s discussions with Nicolae Ceaușescu, leader of Romania; and the Iranian diplomats using their cultural links with the French Communist Party as a back-channel to Hanoi. For the Iranian opposition, the anti-colonial aspect of the war, and its portrayal as a continuation of Vietnam’s war against the French, was often emphasized. Vietnam was one of the global questions that helped unite the opposition despite widely different takes on the Cold War that pitted different strands of leftists, nationalists and Islamists against one another. After the victory of the Islamic Revolution and suppression of the left, many on the left justified their socialism by reminding their Islamist rulers that they had all once backed Vietnamese communists together. By a study of Iranian contributions to the Vietnam War, this paper highlights the south-to-south connections that animated the Iranians’ participation in the global Cold War. It argues that Iranians on both sides of the conflict (Shah and the opposition) were independent actors in Cold War’s intersection with decolonization and made meaningful contributions that are often elided in superpower-focused narratives.