The present study contributes information to the testicular development and reproductive aspects of Glossogobius giuris (Hamilton 1822), one of the target fishes in the Mekong Delta. Trawl nets were used to monthly collect fish specimens from January to December 2020 in four sites along Bassac River, from Cai Rang, Can Tho (CRCT) to Long Phu, Soc Trang (LPST), Hoa Binh, Bac Lieu (HBBL) and Dam Doi, Ca Mau (DDCM). Data analysis of 632 Glossogobius giuris individuals showed that five-stage of sperm development was found in testis histological slides. At stage IV of the testis, different phases of the sperm were observed, indicating that it is a multi-spawner, releasing sperms many times during the breeding season. Further analyses of the testis about apparent frequency and gonadosomatic index showed that this goby can release sperms monthly with a peak in the main wet season. The length at first maturity was observed at 7.24, 7.18, 7.43, and 6.57 cm of TL in CRCT, LPST, HBBL, and DDCM, respectively. The findings contribute essential information to fish population management and sustainable exploitation.