Abstract: New record of species from an unexplored area extends its range of distribution and provides valuable information for the biodiversity conservation and management. Here we reported a brachyuran crab, Baruna trigranulum, for the first time from the Sungai Brunei Estuary, Brunei Darussalam (Northwest coast of Borneo). This small crab is found inhabiting in the crevices of mangrove roots, clumps of mussels, barnacles and rotting wood at the intertidal zone of Estuary. The species is widely distributed in the Indo-Pacific region particularly in Southeast Asian countries and Australia. Distribution of the species along the Estuary is also noted.