Although classified as a dispensable amino acid, glycine serves critical functions in fish metabolism, including antioxidant defense and immune modulation. This study was conducted to evaluate the effects of varying dietary glycine levels in practical diets of growout-stage red drum (Sciaenops ocellatus). Six experimental practical diets were formulated on an iso-nitrogenous (40 g 100 g-1) and iso-lipidic (10 g 100 g-1) basis with glycine supplementation from crystalline glycine at 0, 0.5, 1, and 2 g 100 g-1, and intact protein (gelatin) at 2.50 and 5.0 g 100 g-1, resulting in total dietary glycine levels of 1.99, 2.47, 2.94, 3.89, 2.43, and 2.86 g 100 g-1, respectively. A 12-week growout-stage trial was conducted in a clearwater recirculating system, stocked at 15 fish tank-1 (~17 fish m-2) with initial weight of 111.30 ± 1.26 g. Preliminary results at 10-week showed no statistically significant differences among treatments for growth parameters (P > 0.05). Average weights ranged from 289.11 to 312.00 g (P = 0.511), with weight gains of 178.44 to 200.27 g (P = 0.561) and percent weight gains of 161.27-179.28 % (P = 0.656). Feed conversion ratios varied from 1.40 to 1.52 across diets (P = 0.626). A dose-response pattern was observed with the highest glycine inclusion level (3.89 g 100 g-1) from crystalline source achieving numerically highest final weight and weight gain, despite differences not reaching statistical significance (P > 0.05). Although preliminary data showed no significant differences in growth performance, final data collection and comprehensive analysis of plasma glycine concentrations and serum biochemical parameters are currently underway and may provide additional insights into the physiological effects of dietary glycine supplementation in growout-stage red drum.