The hybrid grouper aquaculture industry is presently constrained by a scarcity of empirical data on growth profiles, particularly during the critical grow-out phase. Concurrently, there is a notable gap in knowledge regarding the optimal protein levels in formulated diets for these stages. With the juvenile phase being the primary focus of existing studies, the grow-out phase remains largely unexplored, leading to suboptimal feeding strategies and potential hinderance of aquaculture productivity. In addressing this informational void, the present study was designed to investigate the impact of varying dietary protein levels on the growth performance of hybrid grouper during the grow-out phase. An 8-month feeding trial was conducted at the grow-out stage to determine the effect of different protein levels (35%, 40%, 45%, and 50%) on the growth of hybrid grouper with low-cost fish was fed to control treatment. Ten fishes with an average initial body weight of 336.0±0.07 g was distributed in 1m X 1m X 1.7m sea net cage in duplicate (n=10). The primary protein sources that were used were fish meal, soybean meal, and corn gluten meal and the primary lipid source were fish oil and sunflower oil. After 8 months of feeding trial, although the control (fed with low-cost fish) shows the highest growth rate, however, among the treatment of different protein levels, T50 shows better overall body weight gain. Moreover, among the treatments with different protein levels, T35, T40, and T45 show no significant difference (p>0.05) but there is a significant difference between T35 and T50 (p<0.05). As for the specific growth rate (SGR), the value increases accordingly (T35:0.29, T40:0.32, T45:0.39, T50:0.48) as the protein level increases (p>0.05). On the other hand, the results for body indices show that there were no significant differences for HSI%, VSI%, and IPF% between treatments (p>0.05). By giving industry participants data-driven insights into managing hybrid grouper nutrition, this study lays the groundwork for improving feeding strategies, aiming to make aquaculture more sustainable and profitable.