Otoliths played essential roles in fish growth determination but were limited to gobies living in the Mekong Delta, Vietnam (VMD). This study consequently lasted for one year from January to December 2020 in order to provide knowledge of morphology and mass of otoliths and their roles in growth determining for a commercial goby Glossogobius giuris in VMD. Samples were monthly collected using trawl nets in four locations from the fresh to brackish waters, including Cai Rang, Can Tho (0‰); Long Phu, Soc Trang (24.9‰); Hoa Binh, Bac Lieu (30.4‰) and Dam Doi, Ca Mau (30.8‰). Data analysis results of 1,291 individuals showed that the otolith mass was similar between left and right sides, but varies with gender, fish size, season and site. Due to high determination parameters, the otolith mass had positive relationships with fish dimension measurements such as weight, total length, eye diameter, body height, and head length. The findings showed otolith mass could be used as a growth indicator for this species.