A 41-year-old woman had undergone cyst-to-duct anastomosis for a congenital biliary dilatation when she was 3-yearold. After 38 years, she presented with a high fever, and laboratory findings showed elevation of liver and biliary enzyme levels. A CT scan showed a mass lesion in a choledochal cyst, and an adenocarcinoma was found in the anastomosis of the choledochal cyst and duodenum. We diagnosed distal bile duct cancer and performed SSPPD after neoadjuvant chemotherapy( gemcitabine plus cisplatin plus S-1). The resected tumor was pathologically diagnosed as papillary-infiltrating adenocarcinoma( ypT2N1M0, ypStage II B). Currently, 9 months after the second surgery, the patient is doing well without any signs of recurrence. The current case suggested the necessity of postoperative lifetime follow-up for patients with bile duct cancer who have undergone radical cyst excision for a congenital biliary dilatation.