Reduced deformability of both infected and uninfected red blood cells (RBC) contributes to pathogenesis in falciparum malaria. Whole blood RBC-deformability is not well-characterised in vivax malaria. We used a laser-assisted optical rotational cell analyzer to measure the RBC deformability in fresh whole blood from Malaysian patients with vivax malaria (n=25). Deformability of whole blood RBC, the vast majority of which were uninfected, was reduced in vivax malaria compared to controls (n=15), though not to the same degree as in falciparum malaria (n=90). Reduced RBC-deformability may contribute to the pathogenesis of vivax malaria, including splenic retention of uninfected RBC.