A choledochocele is an expanded sac of the duodenal side of the distal common bile duct (CBD), and is categorized as a type III choledochal cyst. Unlike other choledochal cysts, it can be easily overlooked because of its very low prevalence, non-specific clinical symptoms, and lack of distinctive radiological findings. However, a patient having a repeated pancreaticobiliary disorder with an unknown origin, frequent abdominal pain after cholecystectomy, or repeated non-specific gastrointestinal symptoms can be suspected as having a choledochocele, and a more accurate diagnosis can be achieved via endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic ultrasound. Because it rarely becomes malignant, a choledochocele can be treated via endoscopic sphincterotomy (EST) and surgical treatment. The authors were able to diagnose choledochocele accompanied by a stone in a patient admitted to the authors’ hospital due to cholangitis and pancreatitis. The patient``s condition was suspected to have been caused by a distal CBD stone detected via multiple detector computed tomography and ERCP, and was successfully treated via EST.