Understanding primate assemblage structure in small protected areas is important for effective conservation planning, particularly in biodiversity-rich regions such as Malaysian Borneo. This study assessed primate species composition, encounter rates, distribution and site occupancy in Tanjung Datu National Park (TDNP), Sarawak. Systematic diurnal and nocturnal surveys were conducted from July 2023 to February 2024 along four main trails, covering 420 survey hours and approximately 8.9 km of transects. A total of 226 individuals, representing eight species from four families were recorded. Macaca fascicularis showed the highest encounter rate, followed by Trachypithecus cristatus. The Critically Endangered Bornean banded langur (Presbytis chrysomelas chrysomelas) was detected across all survey site, but occurred at relatively low encounter frequencies. Species richness and diversity indices indicated moderate variation amongst sites, although the differences were not statistically significant. Riverine and coastal forest habitats supported the highest primate diversity. The occurrence of several threatened species highlights the conservation importance of TDNP within an increasingly fragmented coastal landscape. These findings provide important baseline information for future primate monitoring and support improved conservation management and sustainable nature-based tourism planning in the Park.