Hepatic carcinosarcoma (HCS) is defined as a malignant tumor containing an intimate mixture of carcinomatous and sarcomatous elements. Here, we report the case of a 72-year-old man who developed HCS from an otherwise normal liver. The patient had no history of alcohol abuse or hepatitis B or C infection. An enhanced abdominal CT scan revealed a 9-cm heterogeneous tumor, with enhancement during the arterial phase and delayed wash-out in the latter phases. Also, a marked elevation in alpha-fetoprotein level (15,164 ng/mL; normal range, < 10 ng/mL) was noted. He underwent resection of liver segments V and VI under a pre-operative diagnosis of atypical hepatocellular carcinoma (HCC). The diagnosis of HCS was made based on thorough pathologic examination with a panel of immunohistochemical staining. Following surgery, the patient made an uneventful recovery, and at present, 16 months post-surgery, he remains well with no evidence of tumor recurrence. In conclusion, pre-operative diagnosis of HCS is difficult and radical resection in the early stage is encouraged to improve the prognosis of these patients.