Chitin, a polymer of N-acetylglucosamine, is rich in insect. While insect protein is used as feed ingredient, the nitrogen content in chitin may lead to the overestimation of its actual protein content that analyzed by Kjekdah method. Our present study aimed to evaluate the actual protein level in mealworm meal and its potentiality to replace dietary fish meal for giant grouper (Epinephelus lanceolatus). The crude protein and chitin content in the mealworm meal were analyzed to be 74.63% and 13.21%, respectively. After correction with nitrogen content in chitin, the actual protein of mealworm meal was 69.29%. Based on the results, dietary fish meal protein was replaced by mealworm meal at 0%, 10%, 20%, and 30%. Total of four experimental diets were each fed to triplicate groups of juvenile grouper (initial weight: 20.65 ± 0.08 g) in a recirculation system for 8 weeks. Weight gain, protein retention, protein efficiency ratio, feed efficiency, survival, plasma triglyceride and cholesterol concentrations were not significantly (p>0.05) affected by the dietary treatments. The fish in-fish out ratio decreased from 1.82 to 1.37 while the replacement level increased from 0% to 30%. The oleic acid (C18:1n9) and monounsaturated fatty acids (ΣMUFA) significantly increased in muscle with the increasing dietary levels of mealworm. Results indicated that the mealworm meal can replace dietary fish meal protein up to 30% for giant grouper without any negative effect on growth performance. The use of mealworm meal to replace fish meal can reduce the consumption of marine resource and achieve the goal of sustainable aquaculture.