Obesity is a metabolic disorder, which has become an epidemic worldwide. Bariatric surgery and extended lifestyle adaptation are currently the most effective and long-lasting methods of weight loss. Physical activity (PA) is an essential element of the medical management of patients which subsequent bariatric surgery. Aim of the study: evaluate the effectiveness of physical activity program for bariatric surgery patients. Subjects and method: Quasiexperimental (pre-posttest) research design was used. The study included 70 patients from outpatient's surgery clinic Assiut University Hospital. An interview structured questionnaire was used which included personal characteristics, medical history, and an International physical activity questionnaire. The study was carried through 3 stages: preparatory, implementation, and evaluation stage. Results: There was a highly statistically significant difference (Pvalue=0.000) between the mean score of pre and post-test physical activity program. It showed that 1.4 % of studied patients had high physical activity in the pretest while in posttest 35.7% had high physical activity. Conclusion: Physical activity instructions in the postoperative management of patients appear to increase physical activity and maintain weight loss after bariatric surgery. Recommendations: Further studies are needed to confirm these hypotheses with a larger sample size.