A 70-year-old man was admitted to the hospital because of sudden, upper abdominal and back pain. Laboratory and image data indicated acute pancreatitis. Shortly after the admission, pancreatic and liver abscess with bacteremia developed. Antibiotic therapy seemed effective. A month later, spontaneous fistulization of the pancreatic abscess to the duodenal bulb was found by gastroduodenal fiberscopy. Injection of contrast medium into the duodenal orifice showed that the fistula was draining the abscess and that no other fistula formed from the abscess. Endoscopic retrograde cholangiopancreatogram indicated no fistula formation to the pancreatic duct. The pancreatic abscess became smaller and was not visible using computerized tomography and ultrasonography 3 months later and thereafter. Closure of the duodenal orifice was ascertained by the endoscopy. It is suggested that retrograde infection from the fistula was prevented by the single fistulization to the acidic duodenal bulb, which is not supposed to allow most bacterial growth. Pancreatic abscess usually necessitates operative treatment, even with fistulization to the alimentary tract. It seems likely that the single, small fistulization to the bulb, in addition to the lack of underlying disease and medical and nutritional support, facilitated the spontaneous healing process.