Feeding habits of the bonnethead shark, Sphyrna tiburo were investigated through analysis of stomach contents of specimens collected in shallow waters in northern Brazil (Maranhão State). The diet is dominated by crustaceans, consisting mainly of three species of Callinectes crabs. The species shows a specialist behaviour, preying on few prey items. The percentage of empty stomachs is similar to those recorded in the Northern Hemisphere. Males and females show a similar food spectrum. No important dietary shift was associated with size. However, the importance of Callinectes in food contents differs with size and sex. Size selectivity of prey was not observed. Mean prey weight increased in females up to 90 cm, whereas in males it decreased with length up to 80 cm. Males have less food in their stomachs than females.