Annular pancreas (AP) is a rare congenital anomaly, usually present in childhood, with symptoms due to duodenal obstruction; however, this condition can manifest in adulthood with abdominal pain, pancreatitis and pancreatic head mass. The authors present a case of AP observed in a 22-year-old patient that presented an unusual dual-phase clinical manifestation of duodenal obstruction in infancy that was treated by a duodenojejunostomy, and abdominal pain due to chronic pancreatitis in the adult age. MRI with cholangiopancreatography played a decisive role in achieving the correct diagnosis. The patient was treated by a pylorus-preserving Whipple procedure, with resection of the previous duodenojejunostomy. Pancreatic changes characteristic of chronic pancreatitis were demonstrated both in the AP and in the resected pancreatic segment. A marked biliopancreatic ductal anomaly not previously described in the literature was demonstrated by radiologic examination of the surgical specimen. The pathogenesis of AP, the importance of its association with benign and malignant pancreatic disease and the treatment alternatives are discussed by the authors.