The current study aimed to evaluate the effects of betaine on the growth performance, blood parameters, and histopathology of growing lambs offered fresh or saline water. A total of 20 healthy Ossimi male lambs, aged 9 months, were randomly assigned to four treatments (n=5). Lambs received NaCI (0% or 1.5%) with drinking water and betaine (0 or 2500 mg/kg diet) with ration. The experiment lasted 135 days. Saline water significantly decreased (p<0.01) lamb body weight, blood urea, sodium and alanine amino transferase. Betaine significantly increased (p<0.05) lamb body weight, Hb concentration, RBCs count and hematocrit value. However, betaine decreased (p<0.05) blood neutrophils, band cells and eosinophils, urea, and both alanine and aspartate amino transferases. Saline water induced swelling and disarrangement of hepatocytes, focal medullary tubular necrosis and calcium calculi in renal tissue, and fasciculation and focal lysis of cardiac muscle fibers. In contrast, betaine ameliorated these harmful effects of saline water. In conclusion, dietary betaine could enhance the growth performance and ameliorate the harmful effects of drinking saline water for sheep.