In periurban Costa Rica, undocumented Nicaraguan migrant women are regularly denied medical services from the state health system historically renowned for universal access. Yet Costa Ricans portray migrant women as demanding and disproportionately at fault for health system declines. Medical citizenship is under constant negotiation when undocumented migrants attempt to access state-provided services within this south-to-south migrant circuit. In this article, I draw on 13 months of field research and 138 in-depth interviews with multiple stakeholders to explore the negotiations over the meanings and experiences of medical citizenship. The case study underscores the importance of medical citizenship for a growing number of south-to-south migrants, and theoretically, the gendered dimension of a critically interpretive medical anthropology as well as the limits of biosociality for undocumented south-to-south migrants. The ethnographic details of undocumented migrant Isabel's struggles to procure postoperative care interweave the article to reveal how migrant–provider interactions articulate with broader historical processes of Costa Rican health and economic reform.