Renal cell carcinoma (RCC) is the most common malignancy of the kidney. It is not commonly form tumor thrombus in the ureter or renal pelvis. A 29-year-old woman presented with asymptomatic gross hematuria. Contrast CT study revealed a tumor suspected to be a Transitional Cell Carcinoma (TCC). However, tumor thrombus was found in the renal pelvis and ureter. We performed Nephroureterectomy, bladder cuff excision, and lymph node dissection, and the tumor was diagnosed histopathologically as RCC. We report a very rare case of thrombus-like tumor of renal cell carcinoma mimicking transitional cell carcinoma of kidney.