The southern rough shrimp Trachysalambria curvirostris is a small-sized penaeid shrimp inhabiting coastal waters of the Indo-West Pacific and eastern Mediterranean Sea. It is commercially important as a target species mainly for small-scale bottom seiners and trawlers in Japan, Korea, China, and Taiwan. In Kagoshima Bay, southern Japan, this species is one of the most dominant species in the benthic community. The reproductive biology of T. curvirostris including ovarian maturation, size at sexual maturity, and spawning season was investigated in Kagoshima Bay. A total of 5,681 female specimens were collected during June 2002 through December 2005. Ovarian maturity stages were divided into three categories (undeveloped, developing, and early ripe or ripe) based on the visual observation of ovaries fixed with 10% formalin and oöcyte diameter. The size at sexual maturity was estimated to be 17.3 mm in carapace length. The gonadosomatic index (GSI) showed a significant increase with progressing ovarian maturity stage and most of the females with GSI ≥ 6% were found to be matured. Percentage occurrence of mature females and inseminated females showed similar seasonal trends and the spawning season was estimated to last from May to November, with a peak during June and July.