The aim of this study was to evaluate the effect of total ammonia (TAN) on growth, survivability, some blood biochemistry and histological evaluation of the kidney, liver, skin and muscles of red tilapia fingerlings for 56 days. A total of 180 fish were held at a rate of 10 fish fiberglass -1 tank with capacity of 100 liters welled water (salinity 27.3 ppt). Treatments of 0.1, 0.9, 1.8, 2.9 and 3.5 mgL -1 of TAN were carried out in this study. Fish fed pellets containing 34.7% crude protein. The results showed that fish exposed to 3.5 mg TAN L -1 recorded the lowest final body weight and survival rate, these results inversely related with increasing TAN levels. Fish subjected to treatment of 3.5 mg TAN L -1 achieved the highest values of serum urea, uric acid and creatinine. The histological investigation of kidney, liver and skin of fish exposed to 3.5 mg TAN L -1 showed severe damages in renal tubules, large amount of hemorrhage between renal tubules, vacuolation in hepatic cytoplasm, hepatic congestion, hepatic necrosis, laceration of skin, inflammation in muscle fibers and splitting of large muscle fibers. Based on the results of the present study, it is recommended that increased levels of ammonia should be avoided and eliminating the causes in aquaculture ponds in order to obtain the highest production performance and increase survival rates and maintain fish health and vitality.