Postoperative upper gastrointestinal bleeding, though rare, is a potentially fatal complication of gastric bypass surgery that usually occurs a few months postoperation. The current report describes a 57-year-old man with a bleeding duodenal ulcer who underwent Roux-en-Y gastric bypass surgery 12 years earlier. With an increasing number of gastric bypass surgeries performed each year, physicians must be aware of their patients' altered gastrointestinal anatomy and physiology-as well as the potential for pathophysiology.