A 64-year-old man presented with right renal cell carcinoma with tumoral thrombosis in the inferior vena cava. Transthoracic echocardiography and contrast-enhanced computed tomography 2 days before the scheduled surgery revealed a tumoral thrombus floating in the right atrium. The tumoral thrombus measured 2 by 3 centimeters and the patient was asymptomatic. An emergency surgey was performed to remove the tumoral thrombus from the right atrium and a temporary inferior vena cava filter was placed. Right nephrectomy and thrombectomy were carried out 3 weeks later. Pathological diagnosis made from both surgical specimens was clear cell renal cell carcinoma, and the tumoral thrombus was considered to have separated from the tumor thrombus in inferior vena cava. No obvious recurrence has been observed for 6 months after the surgery.