Double pylorus is a rare gastrointestinal abnormality in which there is fistulous communication between the gastric antrum and the duodenal bulb. A case of acquired double pylorus caused by penetration of a duodenal bulb ulcer into the antrum of the stomach is reported. The patient was a 72-year-old man who had been managed medically at a nearby clinic. Because of increasing epigastric pain, an upper gastrointestinal series was done and he was admitted as on emergency patient to our hospital, with suspected duodenal ulcer perforation. After hospital admission, both upper gastrointestinal contrast study and fiberoptic endoscopy were repeated, and he was diagnosed as having double pylorus. However, X-ray film findings indicated that a part of the fistula penetrated into the abdominal cavity. Billroth II gastrectomy was performed for early treatment on the 10 th day after admission. After histological examination of the surgical specimen and observations of the clinical course, it was thought that the fistula was created by a duodenal ulcer lesion.