A 19-year-old woman with general fatigue who initially consulted a local hospital was referred to us for further examination of jaundice. Contrast-enhanced CT revealed apparent dilatation of the bile duct. Gastrointestinal endoscopy exhibited a tumor of the papilla of Vater(adenocarcinoma, tub2). Thus, pylorus-preserving pancreatoduodenectomy with D2 lymph node dissection was performed. Pathologically, she was diagnosed with a T3bN1M0, pStage ⅡB tumor. After surgery, the patient underwent adjuvant chemotherapy containing S-1 for 6 months. We herein report a juvenile case of ampullary region carcinoma that was successfully treated.