Necrotizing enterocolitis (NEC) carries one of the highest mortality rates of all gastrointestinal disorders. Both its pathogenesis and aetiology remain enigmatic in adult patients. We report on the first known case of NEC following Roux-en-Y gastric bypass (RYGB) long-term. A 42-year-old female patient (BMI 51.2) underwent RYGB. At 12 months follow-up she presented with diarrhea, vomiting, tachypnoea and hypotension. She was severely acidotic (pH 6.9), white cell count (24x109/L) and lactate (7.3U/L). CT presented dilated bowel most prominently at the upper jejunum and she subsequently underwent laparotomy for small-bowel resection, subtotal colectomy and end ileostomy. Intraoperative, patchy necrotic segments of colon were noted. Postoperatively, her lactate increased to 10U/L, necessitating relook laparotomy for further bowel resection. Caecal and ascending colon samples showed ischaemic and necrotic areas with transmural inflammation and marked bacterial overgrowth with no evidence of vascular compromise. These features resembled acute NEC. Clostridium, Campylobacter, Salmonella, Shigella and vasculitis screening were negative. She had a slow recovery, requiring total parenteral nutrition and at 36 months follow-up she is making good progress. We believe an episode of binge eating led to gastrointestinal dilatation as seen in anorexia nervosa following rapid diet change. Such dilatation would diminish blood flow and damage mucosal integrity through ischemia, permitting invasion of pathogenic gas-forming bacteria. With no specific diagnostic criteria; delayed diagnosis, time to surgery and failure to resect all necrotic tissue exemplify the challenges in management. We believe it’s important to highlight this case to raise awareness of similar presentations in post-bariatric surgery patients.