Background: Intraductal papillary mucinous neoplasm of the bile ducts (IPMN-B) is a rare malignant tumor originated from the epithelium of the bile duct. It can secrete a large amount of mucin to cause biliary obstruction. This disease has just been recognized in recent years.Case presentation: We found a 60-year-old woman with intermittent right upper abdominal pain. Imaging examination showed that the left intrahepatic bile duct was dilated with a solid mass. We had left hepatectomy. During the operation, there was colloidal mucus in the bile duct. There was a papillary mass on the wall of the bile duct. -to have developed into invasive adenocarcinoma. At a postoperative 6 months follow-up, the patient had no recurrence and is in good conditions. Conclusion: In our case, IPMN-B has underwent a malignant transformation at the early stage. Therefore, we think that surgical resection should be done as early as possible after the diagnosis of IPMN-B, so as to get a favorable prognosis.