An 80-year-old man visited another doctor with a complaint of fever. A blood test showed hepatic dysfunction and abdominal contrast-enhanced CT revealed dilatation of the common bile duct and intrahepatic bile ducts and a poorly contrasted mass in the distal bile duct. He was referred to our department for surgical treatment. Endoscopic retrograde cholangiography revealed a 5 cm stenosis in the distal bile duct and bile juice cytology showed class IV. The patient was diagnosed with distal cholangiocarcinoma cT2N0M0 cStage IB and underwent pancreaticoduodenectomy and regional lymph node dissection. Histopathological findings revealed a spindle cell-dominated, circumferential tumor in the distal bile duct. Immunohistological staining showed that the tumor cells were positive for epithelial markers (CK and CAM5.2) and a mesenchymal marker (vimentin), and the final diagnosis was “so-called sarcomatoid carcinoma”. The patient received gemcitabine as adjuvant chemotherapy for six months and has been alive without recurrence for one year postoperatively.