Renal cell carcinoma with inferior vena cava tumor thrombus can be misdiagnosed as an inferior vena cava thrombosis if not evaluated carefully with imaging. We describe a case of renal cell carcinoma with inferior vena cava tumor thrombus that was initially misdiagnosed as an inferior vena cava thrombosis due to a possible hypercoagulable state. After 7 months of anticoagulation therapy with no improvement, a right radical nephrectomy and thrombectomy was performed without cardiopulmonary bypass, and a diagnosis of papillary renal cell carcinoma with a level-IIId tumor thrombus was confirmed with no presence of a bland thrombus. We demonstrate the complexity of identifying and treating renal cell carcinoma with venous tumor thrombus and the importance of differentiating between a malignant thrombus and a bland thrombus.