We analyzed diet and prey selection of the relatively unknown albicaudatus subspecies of the White-tailed Hawk (Buteo albicaudatus). Our study was based on an analysis of 259 pellets collected from September 2000 to September 2001 in the municipality of Juiz de Fora in southeastern Brazil. We also assessed the abundance of small mammals with pitfall traps (2,160 trap-nights). Small mammals composed 52.5% of the estimated biomass consumed by the hawks, and selection appeared to be mediated by abundance. The Bonferroni confidence intervals procedure revealed that when abundance of small mammals was higher, the hawks were selective, preying on Calomys tener more than would be expected by chance (P < 0.05); other rodents were consumed less than expected. Oligoryzomys nigripes, Oxymycterus sp., and Gracilinanus spp. were taken in the same proportion as they were found in the field. During reduced prey abundance (October–March), White-tailed Hawks preyed opportunistically on small mammals. Differences in habits and vulnerability of small mammals may explain prey selectivity in the White-tailed Hawk.