Significance During blood-stage development, the malaria parasite replicates inside erythrocytes of the vertebrate host, where it engulfs and digests most of the available hemoglobin. This results in release of the oxygen-binding prosthetic group heme, which is highly toxic in its unbound form. The parasite crystallizes the heme into an insoluble pigment called hemozoin, a process that is vital for parasite survival and which is exploited in antimalarial therapy. We demonstrate that the parasite uses a protein called PV5 in hemozoin formation and that interfering with PV5 expression can increase the parasite’s sensitivity to antimalarial drugs during blood infection. An improved understanding of the mechanisms underlying heme sequestration will provide valuable insights for future drug development efforts.