This report presents the case of a 30-yr-old woman with BA who developed incidental cholangiocarcinoma following the Kasai operation. She showed progressive liver dysfunction and cirrhosis at the age of 30 yr and underwent LDLT. A 4-cm-diameter liver tumor in the anastomotic site of portoenterostomy was incidentally found as a result of a pathological examination of the explanted native liver. The tumor was pathologically diagnosed to be intrahepatic cholangiocarcinoma. Although cholangiocarcinoma in patients with BA has been previously reported in only three cases, it should be nevertheless always considered in the differential diagnosis of hepatic tumors during a long follow-up course in patients with BA.