Rupture of a hepatocellular carcinoma (HCC) is a well-known cause of death in patients with HCC. This report describes a rare case of HCC presenting as cardiac tamponade caused by a spontaneous rupture of mediastinal lymph node metastasis into the pericardial space. A transcatheter arterial embolization (TAE) of internal thoracic artery successfully controlled the bleeding, and the patient was rescued from cardiac tamponade. Although there was no rebleeding, the patient died from liver failure 2 months later. An autopsy revealed a poorly differentiated HCC in the liver, lung and mediastinal lymph nodes.