The study aimed to provide information on growth patterns and condition factors affecting the eleotrid fish Butis koilomatodon from the Mekong Delta, Vietnam, as depending on gender, season and sites.  Totally, 1,063 fish specimens (768 males and 295 females) were collected from January to December 2019 along the mudflat and mangroves in the Tra Vinh, Soc Trang, Bac Lieu and Ca Mau Provinces. The weight and total length of this species were significantly different between genders, seasons and sites. The length-weight relationship was positive, being affected by gender, season and study area. The change in growth patterns (negative and positive allometry and isometry) depended on the season and the region since the slope (b) fluctuated from 1.89±0.17 to 3.33±0.10. This species was generally characterised by a negative allometric growth, as b (2.66) was significantly lower than the isometric threshold. The conditional factor of B. koilomatodon was close to the well-being value and was not impacted by gender but depended   season and site variables. These results showed that the species was well-adapted to the habitat and to the dry season.