Retrograde endoscopic or percutaneous transhepatic bile duct drainage is the treatment of choice for palliation of malignant biliary obstruction. An expanding metal stent, Endocoil spiral stent, with strong radial force was developed to solve the problems of other metal stents which include obstruction by tumor ingrowth, migration, and epithelial trauma from the distal hard edges of the stent. A choledochoduodenal fistula is occasionally found during endoscopic retrograde cholangiopancreatiography (ERCP) or barium radiography. Cholelithiasis is suspected to be the leading cause in some endemic areas like Korea but duodenal ulcer is more common in Western countries. The case reported here is of a 78-year-old woman, suffering from vomiting, epigastric pain, and abdominal distension, who had a Endocoil spiral stent in the common bile duct (CBD) for pancreatic head cancer for 8 months. During barium radiograph, a fistulous connection between the proximal second part of duodeum and the CBD was identified.