The size, growth and reproductive biology of the giant mudskipper, Periophthalmodon schlosseri, was studied in the inter-tidal mudflat of a mangrove swamp along a 0.4-0.6 · 5 km stretch of the Sepang coastal waters, Selangor Malaysia. The size ranges of the giant mudskipper specimens caught in the study area were between 10-27.5 cm TL (20.6 ± 3.1 cm) for males and 14.5-28.5 cm TL (21.9 ± 2.3 cm) for females. Male to female sex ratio during the study was 1 : 1.1. The estimated von Bertalanffy growth parameters were L ¥ = 29 cm and K = 1.4 year )1 , with a growth performance index of Ø¢ = 3.1. Otolith microstructure analysis revealed a strong correlation (Female: r = 0.920, n = 35; Male: r = 0.943, n = 41, P < 0.05) between the number of daily rings (number of days old) over the respective size ranges of male (8.5-19.5 cm SL) and female fish (11.8-22.3 cm SL). Four maturity stages were described to follow gonadal development based on external features; these stages were further validated through histological examination of the ovary and oocyte diameter measurements. The gonadal development cycle of P. schlosseri was asynchronous, as marked by the random mixture of early stages oocytes (diameter: 70.7 ± 14.9 lm) to matured stages (356.9 ± 20.2 lm), and had a prolonged spawning season extending from June to October. Monthly fluctuation of the gonadosomatic and hepatosomatic indices for this species was highly correlated (r = 0.126, P < 0.05).