Carotenoids are exogenously sourced pigments that determine plumage coloration in many species of birds. Aside from plumage coloration, carotenoids play a role in mounting an immune response and neutralizing the by-products of cytotoxic activity. We determined whether colorimetric descriptors of carotenoid-based plumage predict infection occurrence of malarial parasites (order Haemosporida, Plasmodium, Parahaemoproteus and Haemoproteus). We captured birds in an area of sensu strictu Cerrado in southeastern Brazil, used PCR to molecularly detect haemosporidian infections and microscopy to confirm all infections. We collected five feathers from the region below the furcula of each individual to retrieve plumage coloration descriptors, namely saturation, carotenoid chroma, hue and the maximum reflectance at the ultraviolet spectrum. We analysed feathers of 58 individuals from three bird species: Lesser Elaenia Elaenia chiriquensis, Flavescent Warbler Myiothlypis flaveola and Red Pileated Finch Coryphospingus cucullatus. Colour saturation and carotenoid chroma predicted the individual occurrence of an infection with malarial parasites. We suggest that infected individuals may trade carotenoid investment between the immune system and plumage coloration, as carotenoid chroma was negatively associated with parasite occurrence. Our results indicate that haemosporidian parasites are important in influencing physiological trade-offs in natural bird populations.