Background Staple-line leak following laparoscopic sleeve gastrectomy is a dire adverse event. While the treatment of acute and early leaks is well established, there is still dispute regarding late and chronic leaks. We describe an endoscopic approach combining septotomy and sleeve stricture dilation for treating late/chronic leaks. Methods Ten consecutive patients with late/chronic proximal leaks were treated at our center. The septum separating the sleeve lumen from the perigastric cavity was progressively dissected over several sessions and the downstream stricture was pneumatically dilated. The technical and clinical success rates were evaluated. Results: All ten patients were treated successfully. Eight patients had sleeve strictures that were dilated in conjunction with septotomy. A mean of five sessions over the course of 43 days was needed to complete treatment. In two patients with a small perigastric cavity and no stricture, septotomy was achieved with through-the-scope balloon dilation of the fistula. No adverse events were encountered. Conclusions Septotomy accompanied by stricture dilation seems highly effective and safe in late and chronic leaks following sleeve gastrectomy.