Background: Obesity is a growing public health concern in developed countries. Bariatric surgery combined with lifestyle modification is currently the most successful weight loss intervention for the treatment of obesity and it's associated with co-morbidities. Aim of the study: Evaluate the health-promoting program regarding lifestyle behaviors among bariatric surgery patients. Method and subjects: Quasi-experimental research design was used. Sample: Purposive sample included 70 patients from out-patients surgery clinic Assiut University Hospital. An interview structured questionnaire was used which included tool I: Socio-economic status scale and tool II: HealthPromoting Lifestyle Profile II (HPLP II). Results: The mean age of patient's was 34.50 ± 12.52 (16.0-65.0), and 55.7% of them were nonworking/housewives. The mean pre-test health-promotion score was significant with the mean post-test (P-value= 0.000). According to the pre-test nutrition subscale, it was 14.74 ± 2.18 while in post-test 22.97 ± 3.08. The physical activity subscale increased from 8.07 ± 0.43 in the pre-test to 17.83 ± 3.82 in the posttest. Also, it was observed that the highest value was seen in health responsibilities (27.17 ± 2.70) while the lowest value was in physical activity (12.49 ± 1.07). Conclusion: There was a noticeable improvement in health promotion subscale score in the posttest which included health responsibilities, physical activity, spiritual growth, nutrition, inter-personal relation, and stress management. Recommendations: Dissemination of healthy lifestyle recommendations and materials about obesity as a part of primary prevention efforts in the health care and community setting .