From 1919 to 1921 sportswriters in a popular Buenos Aires tabloid gleefully unleashed an anti-Brazil campaign rooted in racial invective. This campaign ultimately provoked an international incident involving political and sports authorities, at the highest levels, in both Argentina and Brazil. This article uses this macaquitos affair to explore a larger pattern in which the nascent Argentine popular press disseminated negative racial portrayals of Brazil as a means of affirming a Euro-descended Argentine racial heritage. While this article highlights the mutually constructed notions of racial difference taking place on a transnational scale, it also emphasizes the centrality of mass media and soccer in both countries' efforts to claim racial success. In addition, the macaquitos affair lays bare ongoing conflicts between new, popular mass media of the 1912–30 period and the Argentine state, which in the macaquitos affair moved quickly to suppress these transgressive discourses of national identity.