Metastatic hepatocellular carcinoma (HCC) to the right atrium occurs rarely and may lead to lethal perioperative complications. A 61-year-old female who was about to undergo operation for resection of a right intraatrial tumor thought possibly to be metastatic hepatocellular carcinoma met with sudden protrusion of the tumor from the right atrial wall that sank into the right ventricle during induction of anesthesia. Right ventricular outflow tract obstruction developed and was quickly diagnosed by transesophageal echocardiography. Emergent cardiopulmonary bypass was rushed on the spot and the surgery was completed smoothly. Here we discuss the possible causes of the event and we recommend that special attention should be paid to the anesthetic techniques and proper precaution should be taken in the face of such a risky surgery.