The present study is to investigate the immunological effects of different sub-lethal concentrations of ammonia and trails to control these levels on immunological response by using different protexin probiotic concentrations (Enterococcus faecium). Differential leucocytes count, phagocytic activity, phagocytic index, cortisol level, serum total protein, albumin, globulin, Serum bactericidal activity, Serum lysozome activity and disease resistance against challenge with Vibrioalginolyticus were investigated. Three hundred Fish were divided in to ten equal experimental groups. 1^st group (control) treated with 0.0  mg/l ammonium chloride and fed 0.0 g/kg feed protexin, The  2^nd ,3^rd ,4^th  group treated with 1 mg/l ammonium chloride (Unionized ammonia-Nitrogen 0.01 mg/l) and fed 0.1 g/kg feed, 0.2 g/kg feed, 0.3 g/kg feed of commercial probiotic protexin concentrate respectively. The 5^th, 6^th, 7^th   group treated with 2 mg/l ammonium chloride (Unionized ammonia-Nitrogen 0.02 mg/l) and fed 0.1 g/kg feed, 0.2 g/kg feed, 0.3 g/kg feed of commercial probiotic protexin concentrate respectively. The 8^th, 9^th, 10^th group treated with 3 mg/l ammonium chloride (Unionized ammonia-Nitrogen 0.03 mg/l) and fed 0.1 g/kg feed, 0.2 g/kg feed, 0.3 g/kg feed of commercial probiotic protexin concentrate respectively. Fish fed at 3% body weight per day for ten weeks. Results showed that protexin supplementation adverse significantly the negative impacts of increasing ammonia concentrations on lymphocytes, phagocytic activity, phagocytic index, Serum total protein and globulin, serum bactericidal activity and serum lysozome activity in all treated groups compared to control.  In contrast, neutrophils and albumin/globulin ratio significantly decreased in all treated groups comparing to the control as well as mortality rates after challenging with Vibrio alginolyticus were significantly lower in all treated groups comparing to the control. Results indicated that by increasing the concentration of the protexin probiotic (Enterococcus faecium) results getting better in all examined parameters comparing to control although increasing ammonia concentrations. Best results in the present study were by inclusion of 0.3gm / kg feed of protexinprobiotic in seabass diet which improve the immune statusof seabassto the favor of adverse the stress of increasing the ammonia concentrations.