A 68-year-old male was referred to our hospital because plain computed tomography (CT) showed right hydronephrosis. Contrast-enhanced CT revealed a mass with an irregular margin and poor contrast effect in the lower pole of the right kidney, which invaded the perirenal fat tissues and the area around the inferior vena cava (IVC). Moreover, a thrombus extending from the right renal vein to the IVC was detected, some of which was suggestive of tumor components on contrast-enhanced magnetic resonance imaging (MRI). Biopsy of the renal pelvic mucosa revealed urothelial carcinoma, which was diagnosed as cT4N0M0 renal pelvic cancer. After five courses of neoadjuvant chemotherapy with gemcitabine plus carboplatin, the patient underwent right nephroureterectomy. To avoid tumor cell dissemination into the abdominal cavity, we removed the thrombus and a portion of the IVC were removed en bloc with the right kidney without opening the vein. On pathological diagnosis, the renal tumor was identified as high-grade urothelial carcinoma with sarcomatoid features and squamous differentiation. The tumor invaded the IVC wall through perirenal fat tissues and further developed into a mass in the lumen of the vein. Although the patient was treated with nivolumab as a postoperative adjuvant therapy, he developed liver metastases and local recurrence on the right psoas muscle 6 months after surgery and is currently receiving chemotherapy with enfortumab vedotin.