A 42-years-old woman had undergone operation for cholecochal cyst with gallbladder cancer 9 years ago. Pathology revealed a polypoid mass in the gallbladder with liver infiltration as poorly differentiated adenocarcinoma. Computed tomography, magnetic resonance cholangiopancreatography, and endoscopic ultrasound showed a newly developed suspected solid nodule in the peripheral portion of cystic lesion in the pancreas head. She underwent a pylorus preserving pancreaticoduodenectomy for the suspected mucinous cystic neoplasm of the pancreas. Pathology revealed poorly differentiated adenocarcinoma. The remnant choledochal cyst had developed to cholangiocarcinoma, which mimicked cystic neoplasm of the pancreas.