Twenty carcasses from a small flock of 5000 four-weeks old broiler chickens were submitted to a poultry disease diagnostic clinic in Tehran. At necropsy, 19 carcasses showed the typical lesions of colibacillosis such as pericarditis, prihepatitis and airsaculitis. One case did not show any gross lesion of colibacillosis or chronic respiratory disease (CRD) but the liver had an abnormal size containing a cystic part at the base of right lobe filled with a whitish fluid. In bacteriological culture, proteus was isolated from liver. Histopathological examination revealed multicentric bile duct hyperplasia and cholangiocarcinoma in the liver. Neoplastic cells effaced hepatocellular architecture. Histological examination of the neoplastic areas in the liver revealed cholangiocarcinoma (bile duct carcinoma). This appears to be the first reported case of cholangiocarcinoma in birds in Iran.