The development of the digestive system in rabbitfish Siganus guttatus from day 0 to day 50 post-hatching was characterized by progressive histological and histochemical changes, illustrating the transition from endogenous to exogenous feeding. On day 2, the differentiation of the digestive tract and the emergence of the liver, gallbladder, and pancreas marked the beginning of exogenous feeding, with significant enzyme activity indicating the importance of nutrient absorption. By day 20, the appearance of gastric glands and pyloric caeca alongside increased enzyme activities highlighted the enhanced digestive capability necessary for feeding shifts from zooplankton to Artemia.