Invasion of a renal cell carcinoma thrombus into the inferior vena cava and right atrium is infrequent. Reaching and completely excising a tumor from the inferior vena cava is particularly challenging because the liver covers the surgical field. We report the case of a 61-year-old man who underwent surgery for a renal cell carcinoma of the right kidney that extended into the inferior vena cava and right atrium. During dissection of the liver to expose the inferior vena cava, transesophageal echocardiograms revealed right atrial mass migration into the tricuspid valve. On emergency sternotomy, the tumor embolized into the main pulmonary artery. We used a selective upper-body perfusion technique involving moderately hypothermic cardiopulmonary bypass, cardioplegic arrest, and clamping of the descending aorta, which provided a bloodless surgical field for precise removal of the mass and resulted in minimal blood loss. Our technique might be useful in other patients with tumor thrombus extending into the right atrium because it reduces the need for transfusion and avoids the deleterious effects of deep hypothermic circulatory arrest. Our case also illustrates the importance of continuous transesophageal echocardiographic monitoring to detect thrombus embolization.