ABSTRACT Belontia hasselti is commonly found in the Banjiran Swamp of the Air Hitam River. A study aimed to understand the reproductive biology of B. hasselti has been conducted from February to March 2018. Fish sampling was conducted once / 2 weeks. Parameters measured were sex ratio, gonad maturity level, gonad somatic index (GSI), fecundity and egg diameter. Totally 100 fishes (46 males…