We report a rare case of adenocarcinoma of the minor papilla of the duodenum treated with transduodenal minor papillectomy. A 64-year-old woman was treated for an asymptomatic duodenal tumor detected on gastroduodenoscopy. Endoscopy showed a 15-mm sessile mass in the descending duodenum proximal to the major papilla. The major papilla was a villous 24-mm-diameter polypoid tumor. Histopathologic examination of the biopsy specimen showed tubular adenoma with moderate epithelial atypia. Transduodenal major and minor papillectomies were performed. The orifice of the duct of Santorini and the pancreatic duct were re-approximated to the duodenal wall to prevent acute pancreatitis caused by scarring and stenosis of the duct orifice. Histological findings were consistent with well-differentiated adenocarcinoma limited to the minor duodenal papilla, without infiltration of the duodenal wall submucosa, and confirmed complete resection. The patient had an uneventful postoperative course and has remained asymptomatic, without evidence of tumor recurrence or stenosis of the pancreatic duct orifice, for 4 years.