Mucinous cystadenoma of the gallbladder account for 0.02% of the total number of cases in the hepatobiliary system. By searching the literature from 1900 to 2020, we found 16 cases of mucinous cystadenoma of the gallbladder. The first report of mucinous cystadenoma of the gallbladder was published in 1901 by Bishop. There are only 3 cases of bile duct obstruction caused by gallbladder mucinous cystadenoma extending into bile duct [1]. Meanwhile, the previous literature reports appear lack of complete imaging data. We report a rare case of mucinous cystadenoma of the cystic duct extending into the common bile duct causing biliary obstruction. It is the first case that describes the imaging findings of the disease in detail.