We herein describe the case of a 67-year-old woman with a duodenal ulcer thought to be caused by elevated pancreatic ductal pressure. The patient complained of continuous upper abdominal pain. Her medical history included idiopathic chronic pancreatitis. Endoscopy revealed a huge duodenal ulcer located on the inferior duodenal angle, which had not been seen on endoscopic retrograde pancreatography two months previously. A combination study using endoscopy and contrast imaging confirmed the relationship between the duodenal ulcer and the pancreatic branch duct. To our knowledge, this is the first case of duodenal ulcer thought to be caused by elevated pancreatic ductal pressure.