Purpose: Adjustable gastric banding (AGB) and sleeve gastrectomy (SG) are restrictive bariatric surgeries that are popular in Korea. However, patients often require further conversion surgeries because weight loss failure and surgical complications tend to occur. The aim of this study was to evaluate the feasibility and safety of conversion sleeve gastrectomy (CSG) after failed primary AGB (PAGB) or primary SG (PSG). Materials and Methods: From February 2010 to April 2016, 21 consecutive patients who underwent CSG after failed PAGB or PSG were enrolled in this study. This study was a retrospective analysis of our prospectively collected database. Demographic, intra and post-operative data were collected and analyzed. Results: Twenty-one patients were enrolled in this study. This comprised 20 women and 1 man, with an average BMI of 31.8±7.8 kg/m 2 . Eighteen patients underwent PAGB and 3 underwent PSG. The mean operative time was 243.6±76.8 minutes, and the estimated blood loss was 190.9±233.2 ml. The mean hospital stay was 4.7±1.7 days. The mean follow-up after CSG was 9.3±1.0 months. Two cases developed immediate postoperative complications: one was a stricture (Clavien-Dindo surgical complication grade II) and the other, a pleural effusion (Grade I). Conclusion: CSG is a feasible and safe treatment option after failed PAGB or PSG. Further prospective studies are required to establish the strategy for conversion operations after failed primary restrictive bariatric surgery.