Background: Obesity is becoming a worldwide health problem. Recently, bariatric surgeries are developing to combat with this problem. However, these surgical methods themselves have risks.Objectives: The present study investigated the preventive effect of routine leak test of both gastrojejunal and jejunojejunal anastomoses immediately after laparoscopic Roux-en-Y gastric bypass (LRYGB) surgery against post-operative leak by inexperienced surgeons. Methods: In a prospective interventional study, this research enrolled 52 morbid obese patients with LRYGB from September 2014 to October 2016. After anastomoses, methylene blue and air leak tests were performed and the section line and both anastomosis sites for patency and inspected for air and dye leaks were examined.