Several major complications from endoscopic retrograde cholangiopancreatography (ERCP), including pancreatitis, cholangitis, and hemorrhage have been discussed in detail; however, a few uncommon but severe complications have been reported. We encountered an unusual case of post-ERCP intrahepatic subcapsular biloma. An 89-year-old woman with a 25-mm mass located at the hepatic hilum, suggestive of cholangiocarcinoma, underwent ERCP which demonstrated complete stricture of the common hepatic duct. Subsequently, two plastic stents were placed from the common bile duct to the right and left intrahepatic branches. On day 3, serum inflammatory markers were elevated and computed tomography revealed a large subcapsular fusiform fluid collection in the right liver, consistent with biloma. On day 6, the biloma ruptured and 500 ml of biliary ascites were removed. On day 8, endoscopic nasobiliary drainage via the right intrahepatic branch was performed because of recurrence of biliary ascites. After the procedure, 150 ml of bile was collected through the drain every day and no ascites recurred. We believe that minor injury to the right intrahepatic bile duct due to guidewire manipulation caused the biloma. Biloma may become apparent several days after ERCP, and endoscopic biliary drainage placement adjacent to the bile duct rupture site can stop bile leakage.