Herein we present a 73-year-old man with primary carcinosarcoma of the liver, a rare malignant tumor of the liver. The case was followed up due to HBV-related liver cirrhosis. Regular check-up by ultrasound demonstrated a hyperechoic tumor in the left lobe of the liver, and he was referred and admitted to our hospital. Dynamic CT studies revealed a mostly hypoenhancing hepatic mass with a peripheral ring enhancement. Surgical resection was performed, and the resected tumor was macroscopically a simple nodular type, 3 cm in diameter, with a dense fibrous capsule. Microscopically, undifferentiated cells were dominant in the tumor, while moderately differentiated hepatocellular carcinoma (HCC) were also observed. A transitional zone was noted between the undifferentiated tumor and HCC. Tumor tissue with adenocarcinoma, osteosarcoma and chondrosarcoma were also detected. Immunohistochemical studies demonstrated that tumor cells were HepPar 1 positive in hepatocellular carcinoma, and CK19 and partly CK7 positive in adenocarcinoma. Moreover, CD56, chromogranin A and c-kit were occasionally positive in undifferentiated tumor cells. The diagnosis of carcinosarcoma was made based on the concomitant presence of HCC and sarcomatous components, yet it is noteworthy that various types of tumor cells were observed.