A study was conducted to determine the biological information (size at distribution, carapace width (CW) and body weight (BW)) and size at maturity of male crenate swimming crab, Thalamita crenata at Setiu Wetlands, Terengganu coastal water. Total of 121 samples of male T. crenata were collected from Setiu Wetlands, Terengganu in this study. The mean of CW and BW of males T. crenata was 6.69 ± 0.69 cm (range: 3.89 - 8.19 cm; n = 121). Only the healthy crabs reacted when being approached and having all of their appendages were chosen. Fifty crabs were randomly selected from the 121 samples and 40 crabs were classified as matured male (via morphological characteristics of vas deferens and spermatophore) with the most frequently size range was 7.0 - 7.9 cm CW (55%). This study concluded that the size at maturity (CW50) of male T. crenata occurred at 6.23 cm. Data obtained from this study could be used as the baseline data and useful in management and exploitation of this species for fisheries and aquaculture in Setiu Wetlands, Terengganu coastal water especially and Malaysia coastal water generally.