Comprehensive information on prey availability and diet composition is important to formulate effective conservation strategies. Data on these of large apex predators, the tiger Panthera tigris, leopard Panthera pardus, and dhole Cuon alpinus, are deficient in Kalakkad-Mundanthurai Tiger Reserve, India, which harbors low prey density. Therefore, we investigated how these predators coexisted by partitioning limited food resources. We found that prey selection and activity patterns differed among predators. The leopard (D [Jacobs' preference index] = +0.916) and dhole (D = +0.937) preferred the Indian chevrotain Moschiola indica, whereas the tiger preferred the gaur Bos gaurus (D = +0.937). Biomass of tiger's diet mainly consisted of the gaur (75%). In the dhole, the Indian chevrotain and sambar Rusa unicolor together contributed 91% of biomass, whereas 79% of leopard's biomass was contributed by the Nilgiri langur Semnopithecus johnii and the Indian chevrotain. The leopard and dhole had the highest dietary overlap (O_jk [Pianka Index] = 0.46). The highest activity overlap was found among the leopard, Indian chevrotain, and sambar. The leopard and dhole would compete for the Indian chevrotain, although the competition may be avoided by different activity patterns. Managements of the Indian chevrotain and gaur are critical for conserving large predators in the region.