This study examines the effects of dietary Astaxanthin supplementation on stress physiology, immune response, and growth performance in Nile tilapia (Oreochromis niloticus). Fish were assigned to four groups: one control (group 1) and three experimental groups (groups 2-4), each receiving different concentrations of Astaxanthin and Hydrocortisone incorporated into commercially prepared feed. To induce stress, hydrocortisone powder was administered to groups 2, 3, and 4. Over a six-week trial, fish were fed daily at 3% of their body weight. Growth parameters (length and weight) and physiological and immunological indicators (blood glucose, packed cell volume, total protein, and lysozyme activity) were measured at weeks 0 and 6, with additional baseline sampling conducted after a 24-hour purge period. The study aims to determine whether Astaxanthin supplementation can alleviate stress-induced physiological alterations, strengthen immune function, and enhance growth in Nile tilapia. Results are being analyzed. Findings may provide aquaculture producers with a natural and sustainable alternative to antibiotics for improving fish health and performance under stressful conditions.