This paper addresses the international networks of three Brazilian geographers who were exiled and persecuted after the establishment of a military dictatorship in Brazil in 1964 — Josué de Castro (1908-1973), Milton Santos (1926-2001) and Manuel Correia de Andrade (1922-2007) — whose works had an impact in the international field of critical scholarship in geography and development studies, which remains underplayed in present-day scholarship. Addressing for the first time their unpublished correspondence, whose inventory is ongoing in Brazilian archives, I reconstruct their international work, especially focusing on its constraints, to engage with recent debates on the geographies of internationalism and on international agencies problematizing the concepts of 'international geographies' and 'internationality' of scientific life. My main argument is that the study of informal networks of scientific sociability allows for an understanding of the constraints that institutions and states pose to the internationalization of knowledge, not only through political repression but also through the establishment of 'national schools'. On the other hand, these sources suggest that the exile can play a creative role in stimulating exchanges of knowledge, a concept, on which further research is needed in political geography.