This study aimed to examine the existence of customary law and the interaction of the Kawati customary-law community on Tomia Island to conserve Ole fish, an endemic species thought to be found only on the Wakatobi Islands, Southeast Sulawesi. This study used a descriptive qualitative approach with data analysis involving interviews, focus group discussions, and a review of relevant documents. The results showed that Kawati customary law plays a central role in coastal resource management through rules that prohibit fishing in spawning areas, regulate the use of environmentally friendly fishing gear, and limit fishing time. Customary declarations involving various parties, including traditional leaders, local government, and conservation organizations, strengthen the legitimacy of customary law and create synergy in Ole fish conservation. This indigenous-based approach has proven to be able to maintain the sustainability of marine ecosystems while supporting the social and economic welfare of local communities. This research makes an important contribution to a custom-based marine resource management model that can be applied in other coastal areas.