Hepatocellular carcinoma (HCC) advancing to the right atrium (RA) through the hepatic vein has generally been regarded as a terminal lesion of carcinoma. However, because tumor thrombus (TT) in the RA may cause sudden death by heart failure or pulmonary embolism, it is a pathologic condition that needs emergency extraction. Our case was a 55-year-old male. The HCC had a main lesion in the anterior region of the hepatic right lobe, accompanying TT highly occupying the region from the middle hepatic vein and inferior vena cava to the RA. For this tumor, we conducted an extended right anterior segmentectomy and extraction of the TT in the RA under an extracorporeal circulation. He was discharged on the 28th day after surgery, and at present, when 12 months have passed since the surgery, survives without any sign of its recurrence. There have been eight HCC cases including our case, reported regarding the simultaneous resections of a main tumor and TT under cardiopulmonary bypass. Because two patients among this group of eight survived for more than two years, resection is recommended even for advanced HCC highly infiltrating to the RA.