A 23-year-old man was admitted to our department due to hemorrhage from gastric varices. He had been diagnosed as having Wilson's disease at the age of 17. Abdominal ultrasonography and computed tomography (CT) showed portal thrombosis and a large mass occupying most of the right lobe in the liver. The tumor was diagnosed as hepatocellular carcinoma (HCC) by image views and tumor markers. He died 3 months after the diagnosis, and an autopsy was performed. Histologic examination of the tumor showed moderately to poorly differentiated HCC. The nontumorous lesion of the liver revealed cirrhosis. HBX-DNA sequence was not detected in the liver. Hepatic cirrhosis is a well-recognized complication of Wilson's disease, but HCC is extremely rare. We describe the clinical findings of this patient and discuss the relationship of the development of HCC with a review of the relevant literature.