Abstract. Sulistyorini IS, Poedjirahajoe E, Faida LRW, Purwanto RH. 2018. Social capital role in the utilization of mangrove ecosystem service for ecotourism on Kutai National Park, East Kalimantan, Indonesia. Bonorowo Wetlands 2: 61-68. Social capital has an important role in mangrove ecosystem preservation. Changes to mangrove ecosystem services can affect elements of social capital. Ecotourism is one of the alternatives that can be developed in the mangrove area in the National Park. The purpose of the study was to give an overview of the correlation between several elements of social capital in supporting ecotourism in mangrove areas. This study was conducted in five villages in East Kutai Regency, East Kalimantan, namely Singa Geweh, Sangkima, Teluk Singkama, Teluk Pandan and Kandolo. There were 530 respondents from the five villages involved as informants or resource persons. The data were analyzed by Sequal Equation Modeling Partial Least Square (SEM-PLS) method with SmartPLS. Based on the initial assessment by the scoring method, five social capital, i.e., trust, networking, community involvement, social norm and concern to mangrove had low criteria to support ecotourism in Kutai National Park (KNP) mangrove area. According to SEM-PLS analysis of the social capital variables, community involvement, social norms and trust had negative effect on the ecotourism. Trust and community involvement were relatively low in the four villages (Singa Geweh, Sangkima, Teluk Singkama, and Kandolo). They were associated with social norms. On the other hand, concern to mangrove, education and income levels and networking had positive effect and power to support ecosystem service of mangrove for ecotourism.