A study on population of proboscis monkey (Nasalis larvatus Wurmb.) was conducted in the area of riparian ecosystem of Rawa Gelam, Tapin District, South Kalimantan duringthe period of February-March 2014. The purpose of this study was to determine the condition and the structure of the proboscis monkey population living outside the forest area. Rawa Gelam ecosystem is a cultivation area located on riverbanks of the Puting river. The remaining vegetation at Rawa Gelam contains only a maximum of 200 meters in width, and behind it there were paddy fields and palm oil plantations. The population of proboscis monkeys was counted using Total Count Sampling method. Result of this study showed that the population of proboscis monkeys in Rawa Gelam consisted of nine groups, with the total number of individuals was 192. The population density was 28.34 individuals/km2 with a group density of 1.34 groups/km2. In addition to this species, Rawa Gelam habitat was also inhabited by two other primate species. Seven groups of long-tailed macaques (Macaca Fascicularis) and five groups of langurs (Trachyphitecus auratus) were recorded from this area, with the number of individuals of 47 and 76, respectively. The main threat of proboscis monkey's conservation in Rawa Gelam was habitat destruction and change of habitat function. Proboscis monkeys can be saved from the local extinction through habitat restoration needs to be done by applying agroforestry system and developing integrated ecotourism development.