Trypauchen vagina is a commercial fish, but little is known on its population parameters. This study was carried out at downstream of Hau River in the Mekong Delta, Vietnam to provide fundamental information on the population biology of T. vagina based on length-frequency distribution analysis of 1,527 individuals. The male to female T. vagina ratio was not significantly different within and between seasons, and the parameters of the von Bertalanffy curve of this fish were given as L∞= 24.15 cm, K =0.53 yr-1 and t0 = –0.03 yr-1. The longevity (tmax) and the growth performance (Φ’) were 5.56 yrs and 2.50, respectively. The fishing, natural and total mortalities of this fish were 1.29 yr-1, 1.44 yr-1, and 2.73 yr-1, respectively, and its exploitation rate was 0.53. There were two recruitment peaks in May and October, and relative yield-per-recruit and biomass-per-recruit analyses gave Emax= 0.735, E0.1 = 0.656 and E0.5 =0.384. This gobiid could be potential for future aquaculture due to high growth parameter. The goby stock was subjected to overexploitation so that the mesh size of deep gill nets should be increased and avoiding catch fish during the recruitment period for sustainable fishery management.