Study on feeding and reproductive biology of the goby Eleotris melanosoma distributed along the Bassac river, Mekong Delta was conducted from August 2012 to July 2013. Results showed that E. melanosoma is an omnivore. Feeding ingredient of this species consists of five major groups as the followings: arthropoda, mollusks, small fish, phytoplankton and zooplankton. Results also indicated that gonadosomatic index (GSI) of E. melanosoma was highest from May to October, meanwhile the lowest value of hepatosomatic index (HSI) in July; conditional factor (CF) was less fluctuation especially in male; in female, CF reached the highest value in April and November. The results showed that spawning season of E. melanosoma ranged from May to October, in which the peak of spawning season in October. Fecundity of E. melanosoma ranged from 49 to 930 egg per gram of their body weight (mean=551±363 egg/g). The length of first maturity (L_m) of E. melanosoma is 8.62 cm and 7.79 cm for male and female, respectively.