Access to public health has been, is, and will be a necessary right for any person in the world, motivating the proposal of universalist approaches as the best way to provide this service. However, we know that universalism is limited, at best, when it concerns immigrants. In this article, we focus on Costa Rica’s and Uruguay’s health systems, generally acknowledged as Latin America’s most universal, to argue that there are important barriers that limit immigrants’ access to public health insurance and health care. Applying a model based on the work by Niedzwiecki and Voorend (2019) that allows us to disaggregate the barriers to access into legal, institutional, de facto, and agency barriers, our analysis shows that migration and social policy interact to create barriers of different magnitudes, often conditioning healthcare access on migratory status, formal employment, and/or purchasing power. These limitations to universal social protection create important vulnerabilities, not only for the immigrants involved, but also for the health systems, and therefore for public health, highlighting the limitations of universalism.