We studied the diet of Acanthochelys spixii in a wild population in the Cerrado of central Brazil for 19 months, investigating ontogenetic, sexual, and interindividual variation. The diet consisted mainly of nymphs of Odonata, although other insects, amphibians, and plant material were also present. We observed no ontogenetic shifts in diet composition (e.g., no shift from carnivorous juveniles to herbivorous adults), which can be related to the high abundance of prey at the study site. There was no association between prey size and turtle carapace length, with larger animals still taking small prey. Dietary niche overlap was high, and there was no difference in niche breadth between sexes. However, differences in diet composition suggested differential habitat use, with males using more the periphery and females using more the center of ponds. Diet composition varied more among males than among females, which can result from higher diversity of prey at the pond margins, higher movement rates, or larger home range of males. The high frequency of empty stomachs (41%) reflected life-history characteristics of turtles (e.g., low metabolism, ectothermy, late sexual maturity, and great longevity). The importance of prey categories sensitive to pollution in the diet of A. spixii highlights the integrity of the study sites and the vulnerability of these populations to the rapid degradation of Cerrado biome.