The purpose of this study is to assess the suitability of coastal tourism in the Diyonumo Island and the carrying capacity of the area to support the sustainability development of coastal tourism in the island. The study was conducted at Diyonumo Island, Deme II Village, East Sumalata District, North Gorontalo District, Gorontalo Province, from September to November 2020. The data collection was done by observation and surveys. Study location was divided into 4 stations with an assessment of 3 categories designated for beach tourism, namely recreation, fishing, and camping. Tourism Suitability Index (TSI) and carrying capacity were calculated from the obtained data. The results showed that the island has the potential to be developed into a tourist area with the TSI value for the categories of recreational, fishing, and camping is categorised ‘very suitable’. Moreover, the carryingcapacity for recreation, fishing, and camping are 1.916 people/day, 104 people/day, and 125 people/day, respectively. The most important thing to do in order to achieve a sustainable development and management is by properly use and manage the resource of the island and this effort can be done by government through community empowerment programs.Indonesian title: Pengembangan wisata pantai berbasis potensi dan daya dukung kawasan Pulau Diyonumo, Kecamatan Sumalata Timur, Gorontalo-Indonesia