This study was carried out in four sites along the coastline, including Duyen Hai - Tra Vinh, Tran De - Soc Trang, Dong Hai - Bac Lieu and Dam Doi - Ca Mau, to provide data on the diet composition of Butis butis - a commercial fish in the Mekong Delta, Vietnam. Seven hundred fifteen individual fish (412 females and 303 males) were collected monthly using trawl nets from March to August 2019. The study results showed that Butis butis was a carnivore ingesting Acetes spp., small fish, molluscs, Uca spp., and others (fish scale and detritus). The fish diet composition was affected season (PseudoF=13.07, df=1, p=0.001) and site (Pseudo-F=2.37, df=3, p=0.03) but not sex (Pseudo-F=1.45, df=1, p=0.24). Acetes spp. (Z=-3.96, df=1, pAcetesspp. (8.59, df=3, p=0.35). The diet composition was not regulated by the interaction sex ´ site (Pseudo-F=0.21, df=3, p=0.98) season ´ sex (Pseudo-F=0.06, df=1, p=0.96) and site ´ season (Pseudo-F=0.63, df=1, p=0.69). The findings are the basis for further studies on cultivating this fish in the future.