Background: Nonalcoholic fatty liver (NAFLD) is a worldwide, leading cause of chronic liver disease, not yet approved medical treatment standards. The aim is to assess the effects of aerobic exercise sand calorie-restricted (CR) diet on many clinical and laboratory findings in patients with Nonalcoholic Steatohepatatis (NASH). Methods: In Randomized controlled trial study, in Mashhad, between February 2010-August 2011, Twenty-five patients with NASH, in ranging ages of 18-55, were randomly selected to be divided in to two groups, who received CR-diet and aerobic exercise (n = 12) and CR-diet alone (n = 13). We measured Anthropometric indices, cardio-respiratory fitness, and biochemical profiles in three steps, in baseline, and after 8-12 weeks of intervention. We measured hepatic steatosis and patient's quality of life by ultra-sonography and short form (questionnaire) 36 in three steps. Data was then analyzed by paired and independent samples T Test. Results: We observed a significant improvement in BP, FBS, TG, HOMA-IR, ultra-sonography grading of steatosis and quality of life, only in patients who received aerobic exercises. (P value 0.021, 0.005, 0.006, 0.042, 0.010 and 0.012). Waist circumference, waist-to-height ratio, serum ALT and peak oxygen consumption improved in both groups; however, improvement was significantly, higher in patients who received aerobic exercises (P value 0.027, 0.011, 0.020 and 0.020). Body weight, BMI, body fat percentage and AST improved in both groups but they were not significantly different. No significant changes noted in total cholesterol, LDL and HDL in groups. Conclusions: Add of aerobic exercises to CR diets can, not only enhance the therapeutic effects of calorie-restricted diet, but also bring more benefits in patients with NASH.