The single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S) surgery is technically demanding because of duodenal dissection over the head of the pancreas. However, there have not been any reports of extra-hepatic portal triad injury during duodenal dissection. Herein we report the first case of a portal vein injury during duodenal dissection. Additionally, we attempt to demonstrate the root cause of this intra-operative complication, and how to avoid this type of injury in the future.