Mirizzi syndrome is a rare complication of cholelithiasis, which is defined as a common bile duct obstruction due to stones impacted in Hartman’s pouch or the cystic duct of the gallbladder. The impacted stones and surrounding inflammation can lead to a biliobiliary fistula. We herein present the case of a 73-year-old Japanese man with a biliobiliary fistula that was diagnosed peroral cholangiography (POCS). We performed partial cholecystectomy and choledochoplasty as the stone had eroded almost the entire circumference of the bile duct. Postoperative complications included a minor bile leak from the repaired common bile duct apparent on postoperative day 1, which was managed conservatively. The patient was discharged on postoperative day 9. Based on this experience, POCS is useful for detecting the existence of a biliobiliary fistula in cases of Mirizzi syndrome. Once a biliobiliary fistula is confirmed, it is important to select an appropriate surgical procedure based on the extent of common bile duct involvement in the inflammatory process.