Understanding the fish’s food and feeding habits is essential in aquaculture and research on invasive species. Butis koilomatodon is one of the potential candidates for aquaculture in the Mekong Delta because it can survive in a wide range of water temperature (26–36 °C) and salinity (3.8-37.25%), but data on this fish species’ food and feeding habit are still fragmented and deficient. Consequently, this research aims at supplying necessary data related to diet compositions and feeding activity of Butis koilomatodon collected in six estuarine areas of Mekong delta from April 2019 to March 2020. A total number of 1,227 specimens of Butis koilomatodon (891 males and 336 females) were analyzed diet composition and feeding strategy based on the kinds of food they consumed. The results show that four main food categories were shrimps, small fish, Polychaeta, and detritus, of which the highest frequency of prey is shrimp while the lowest one is Polychaeta. The gender and fish size do not affect this species’ dietary constituent; however, the changes in seasons and sampling sites impact on the diet composition of these species. The shrimps, small fish, and detritus contribute to regulating the food composition of Butis koilomatodon between two seasons and among the six sampling sites. In combination with the modified Costello graphic, all fish specimens’ gut fullness suggested that Butis koilomatodon is a predator with high feeding intensity. The findings can supply the fundamental knowledge about the nutrient biology of Butis koilomatodon and be useful for artificial cultivating this fish.