Simultaneous development of intrahepatic bile duct and gallbladder carcinoma is extremely rare. We report herein the case of an 86-year-old man found to have double cancer of the gallbladder and intrahepatic bile duct. Computed tomography and magnetic resonance cholangiopancreatography revealed a polypoid mass in the gallbladder and dilatation of the intrahepatic bile duct with intraductal papillary tumor in the left side of the liver. The patient underwent left hepatectomy, cholecystectomy with lymphadenectomy around the hepatoduodenal ligament. Pathological examination of the gallbladder revealed undifferentiated giant cell type carcinoma invading the muscularis propria. On the other hand, the liver tumor was intrahepatic intraductal papillary mucinous carcinoma in situ. Therefore, this was an extremely rare case of synchronous carcinoma of the gallbladder associated with intrahepatic cholangiocarcinoma.