We used stomach content and stable isotope analyses to compare diet as a proxy for ecological similarity among 3 tropical sharks, Carcharhinus leucas, C. amboinensis and the Endangered Glyphis spp. Our analyses suggested that all 3 predators consumed mainly teleost fishes but also preyed on crustaceans, cephalopods and reptiles. Diets varied spatially and through ontogeny. Some juvenile C. leucas sourced prey from the same food web as juvenile C. amboinensis, although prey sources varied among C. leucas nurseries. Dietary overlap existed between sympatric adult C. leucas and C. amboinensis, and both species occupied higher trophic positions than juvenile conspecifics. Although sample sizes for Glyphis spp. were small, our results suggested previously undescribed dietary partitioning between this genus and the sympatric C. leucas.