In Indonesia, grouper fisheries play an important role both economically and ecologically. However, stock sustainability is threatened by uncontrolled fishing, especially by small-scale fishermen. The waters of Banggai Laut have high grouper fisheries potential, but the lack of data and studies on the status of grouper catches raises concerns. This study aimed to estimate the catch per unit effort (CPUE) and maximum sustainable yield (MSY) of groupers in Banggai Laut waters. The research method used field surveys and observations. Primary data were collected through direct observation and interviews using purposive sampling. Secondary data were obtained from related agency records and a literature review. The mean CPUE for groupers in Banggai Laut was 0.5395 tons/unit/year, with a mean annual production of 1964.8 tons, and fishing effort of 3592 units/year. The CPUE trend for 6 years (2018–2023) revealed a strong correlation (76.2%) between fishing effort and catch volume. Other influencing factors included seasonal differences and fishing grounds used by each vessel. Based on the Schaefer model, the estimated optimum fishing effort (F) was 1478 units/year with a maximum sustainable catch (CMSY) of 1855.1 tons/year. These results, based on catch values for 6 years, indicate that the number of fishing vessels exceeded the optimum limit F in 2020-2023, resulting in overfishing. Several factors influenced overfishing in grouper fisheries, including the increase in the number of fishing vessels each year, technical aspects of the fishing gear used, including fishing gear that is not environmentally friendly, thereby affecting the productivity.