The present work aimed to study the effect of different doses of oxytetracyclin (0, 40, 80, 120 mg/kg basal diet) and florfenicol, (0, 7.5 , 15 , 22.5 mg/kg basal diet) on growth performance, feed utilization and residual measurements in Oreochromis niloticus. The results revealed that the dose 40 mg oxytetracycline/kg basal diet caused the highest final Body weight, weight gain, specific growth rate, condition factor, moreover it improved feed conversion ratio compared with other doses of oxytetracycline, florfenicol and control group. Also the best protein efficiency was recorded by fish fed the diet 40 mg oxytetracycline/Kg basal diet. The results of determination of oxytetracycline and florfenicol in fish muscle after 10, 21 days were negative results but after 3 months the results were positive and the lowest concentration of antibiotic by fish fed the diet 40 mg oxytetracycline/kg basal diet.