Duplication of the gallbladder is a rare congenital anomaly of the biliary system with the incidence of 1 in 3800. A 38-year-old woman visited our patient clinic for evaluation of wall thickening of the gallbladder, detected by abdominal ultrasonography during a regular medical checkup. Drip infusion cholecystocholangiography-computed tomography revealed Y-shaped duplicated gallbladders.