This chapter explores how the Sociedad Argentina de Escritores (SADE, established in 1928) and the Sociedad de Escritores de Chile (SECh, established in 1931) became actively involved with antifascism in relation to national and international processes connected to the rise of fascism, the Spanish Civil War, World War II, and the Cold War. Each association’s trajectory was specifically shaped by each country’s context. In Argentina, SADE’s politicization unfolded under military regimes, conservative fraudulently elected governments, and Juan Perón’s regime (1946–55). In Chile, SECh’s politicization developed in the context of the governments of the Popular Front (1938–52) and the relative strength of leftist parties. This comparative analysis reveals convergences and differences and highlights the networks that connected writers at multiple levels, providing a new angle on the local and transnational frameworks for the antifascist struggle in the 1930s and 1940s and its transition to Cold War-era divisions.