Cholangiocarcinoma is a predominantly fatal cancer, which can be difficult to treat. We report a 73-year-old man who developed cholangiocarcinoma with cholangiohepatitis and diabetes. Administration of pioglitazone, peroxisome proliferator-activated receptor gamma (PPARgamma). agonist, improved not only diabetic control, but also the tumor-induced cholangiohepatitis, and improved the patient's quality of life. Although he finally died of obstructive jaundice, thiazolidinedione should be considered for treatment of tumor-induced hepatitis in the presence of diabetes, unless severe side effects occur.