Grouper is an important commodity due to its role in ecological balancing and increasing the national economy through foreign exchange on export-import trade. In Ayau Island, grouper management is performed in customary law called Sasi which closes a fishing area during a certain period to improve the harvested yield in the future. Despite many previous studies investigating Sasi law, the financial implications of their application are still unreported. This study aimed to analyze the feasibility of the grouper fishing business in applying customary Sasi law in the Ayau Islands, Raja Ampat Regency, Indonesia. Primary data were obtained from 70 respondents interviewed to assess the financial and institutional aspects, while the direct fishing grounds investigation evaluated the operational and fishing technical side. Secondary data were obtained from literature review- and related agencies. Feasibility analysis was determined based on NPV, ROI, IRR, BCR, and PP value.  The findings showed that most fishermen are between the ages of 31 and 40, with the majority having a moderate level of formal education. Sasi was categorized into six groups based on factors such as location, commodity types, ceremonies, seasonal effects, communal ownership, and the duration of open-closed periods. All economic indicators suggest that the grouper fishing business is viable, with an NPV greater than 0, BCR greater than 1, a payback period shorter than the project life, and ROI and IRR exceeding the discount rate. Several assessment factors demonstrate that Sasi law is profitable for the local economy, and government support is needed to ensure its preservation.