The 1970 election of Salvador Allende as president of Chile gained international attention, as a declared Marxist came to power through elections, offering an alternative to Castro's Cuba. In Argentina, governed by a right-wing dictatorship, the initial fear was transformed into a policy of rapprochement. In the midst of the Cold War, the historical Argentine-Brazilian rivalry was stronger than both military regimes' anti-communism. General Alejandro Lanusse decided to support Allende's Chile to balance Brazil's influence, but also as a way to control the domestic repercussions of Allende's victory, especially the rise of revolutionary slogans and the circulation of guerrillas. This article traces the network of national, international and transnational factors that influenced a surprising bilateral relationship.