This study contributed to investigating the changes in morphometric and meristic variations in Mystus albolineatus at two different sites in the Mekong Delta (VMD). This is a high economic-value fish species in the region. The study was conducted for 12 months (03/2022 - 02/2023) at two sites along the Hau River (a branch of the Mekong River) with different environmental characteristics, including a freshwater site year-round at Cai Rang (Can Tho City) and a site affected by saltwater intrusion during the dry season at Long Phu (Soc Trang province). Fish samples were collected using different fishing gear of various sizes. The results obtained 825 individuals (443 females and 382 males) at both sites (408 at Cai Rang and 417 at Long Phu). Through the analysis process, it was found that the total length (TL) and weight (W) of this fish species were significantly influenced by gender and season. Both parameters were significantly higher in females (TL: 11.13±0.09 SE cm; W: 10.17±0.06 SE g) than in males (TL: 10.68±0.10 SE cm; W: 9.95±0.07 SE g). Meanwhile, during the dry season (TL: 10.15±0.10 SE cm; W: 9.58±0.08 SE g), the fish had lower length and weight compared to the wet season (TL: 11.42±0.08 SE cm; W: 10.39±0.05 SE g). The interaction between gender and season also significantly affected the TL of Mystus albolineatus. In addition, eye diameter (ED), eye distance (DE), body height (BH), head length (HL), ED/ HL, DE/HL, BH/TL, and HL/TL all showed significant differences by gender and season. The results of this study on the morphological characteristics of this fish species indicate that it adapts well to the environment at both research sites. The findings of this study provide basic data on the variation in morphological characteristics of Mystus albolineatus in the VMD region.