This study aimed to explore the impact of adding methionine on growth performance, feed utilization, biochemical parameters, and economic assessment of Oreochromis niloticus. A total of 180 fries were acclimated and then randomly allocated into the experimental aquariums. Fish were distributed across 12 aquaria with 15 fry each, having an initial average weight of 83.50± 0.485g per aquarium. Methionine was incorporated at levels of 0, 5, 10, and 15g/ kg in experimental diets labeled D1, D2, D3, and D4, respectively for 56 days. Growth performance metrics such as total body weight gain (TBWG), daily gain (ADG) and specific growth rate (SGR) increased in the methionine-supplemented groups compared to the control. The mortality rate was 6.67% in the control group, while it was zero in the methionine-supplemented groups. The feed conversion ratio and protein efficiency ratio also improved. Total protein and albumin were higher in all methionine treatments compared to the control group. Levels of AST, ALT, and cholesterol were not significantly affected by methionine supplementation. The highest uric acid level was found in the group receiving 15g/ kg methionine. Fish body composition, including moisture, crude protein, and ash content, showed significant increases. Energy retention (ER%) improved by 6.90 and 21.29% in the groups receiving 10 and 15g/ kg methionine, respectively, compared to the control (D1). Protein productive value (PPV%) improved by 129.06, 142.41, and 151.32% for the 5, 10, and 15g/ kg methionine groups, respectively, compared to the control. The net improvement in feeding efficiency, reflected by a decrease in feeding costs, was 13.85, 25.44, and 31.54% compared to control. Our observations indicate that, including methionine in fish diets enhances performance metrics, increases total protein and globulin levels, improves energy retention and protein productive values, and boosts the net economic benefits of feeding.