Congenital duplication of the gallbladder, including true duplication and septated gallbladder, is an uncommon but potentially complicated malformation. It presents biliary colic associated with acute or chronic cholecystitis. It can be diagnosed preoperatively by various imaging tools such as real-time ultrasonography, biliary scintigraphy, oral cholecystography, or endoscopic retrograde cholangiography. It can be safely managed by either laparoscopic or open procedures. This report describes a 6-year-old girl with true duplication of gallbladder diagnosed preoperatively by real-time ultrasonography and treated by open cholecystectomy.