Malaria parasites are exquisitely adapted for survival within human red blood cells. Understanding how malaria parasites enter human red blood cells is essential for the development of strategies to inhibit blood stage infection. Plasmodium vivax preferentially invades reticulocytes, which are young red blood cells. Successful entry depends on the specific interactions between P. vivax reticulocyte-binding protein 2b (PvRBP2b) and transferrin receptor 1 (TfR1). The PvRBP2b-TfR1 invasion pathway is essential for P. vivax entry into human reticulocytes, as TfR1-deficient erythroid cells are refractory to invasion by P. vivax, and anti-PvRBP2b monoclonal antibodies inhibit reticulocyte-binding and block P. vivax invasion in field isolates. We present a high-resolution structure of a ternary complex with PvRBP2b bound to human TfR1 and transferrin which provides a detailed view of the critical interaction surfaces. While the interaction domain of PvRBP2b is subject to balancing selection, mutational analyses show that PvRBP2b residues involved in complex formation are conserved, providing a promising design strategy to engineer antigens that may be strain-transcendent against P. vivax infection. We are able to demonstrate that PvRBP2b binds to TfR1 using residues that are specific to human TfR1. These functional analyses of TfR1 highlight how P. vivax has hijacked TfR1, which is an essential housekeeping protein, by binding to sites that govern host specificity without affecting its cellular function of transporting iron. Crystal structures of PvRBP2b in complex with antibody fragments have definitively mapped the inhibitory epitopes and define different structural modes of inhibition. Our results establish a structural framework for understanding how P. vivax reticulocyte-binding protein engages its receptor and the molecular mechanism of inhibitory antibodies, providing important information for the design of novel vaccine candidates.