Abstract: Scylla olivacea and Scylla tranquebarica are two mud crabs species that live associated in the wild. This study was done to investigate the mating success between the two species by determination of the duration and recording the process of mating activity. Wild mud crab samples were collected from Terengganu coastal water, Malaysia. Limb autotomy was subjected to female crabs to induce molting before the introduction of male crab for mating trials. Ten pairs of each mating trial were observed. Mating success of control trials of S. olivacea (T1) and S. tranquebarica (T2) is 60 and is 50%, consecutively. Mating success of hybrid trials for male S. olivacea with female S. tranquebarica (T3) is 40% and male S. tranquebarica with female S. olivacea (T4) is 30%. The highest mean duration of pre-copulatory guarding is T3 (12,240 min±1,859.0) while the lowest is T2 (8,064 min±1,287.9). As for copulation, the highest mean duration is T4 (59.3 min±18.0) while the lowest is T1 (59.3 min±18.0). Meanwhile, the highest mean duration of post-copulatory guarding is T2 (312.0 min±50.2) and the lowest is T3 (82.5 min±28.7). Longer duration of pre-copulatory guarding and copulation were observed on hybrid trials (T3, T4) compare to the controls (T1, T2). It has been observed that all successful mating trials in the present study show general mating activity, involving pre-copulatory guarding, copulation and post-copulatory guarding. Result of the present study shows that hybridization can occur in captivity and there are also possibilities of hybridization between the two mud crab species to occur in the wild.