Undifferentiated carcinoma of ureter is rare neoplastic lesion, and the natural history of undifferentiated carcinoma of ureter has not been known well yet. We hereby presented an autopsy case of undifferentiated carcinoma of the ureter with rapid progression from the initial stage. A 62-year-old male visited the local urologist complaining of asymptomatic gross hematuria. Cystoscopy revealed the outflow of hematuria from the right ureteral orifice. Abdominal CT showed the right hydronephrosis with atrophic change of the renal parenchyma and the stenosis of upper ureter. He was referred to our hospital on suspicion of a right ureteral tumor. Magnetic resonance imaging and retrograde ureterography did not reveal a tumor in the right ureter. He complained of low back pain 4 months after the initial hematuria, and CT revealed the diffuse enlargement of the right kidney, swelling of the abdominal lymph nodes, and lung nodules. Renal biopsy was done, and only undifferentiated cells were revealed histopathologically without any specific findings to diagnose the primary organ. The tumor increased progressively, and he died about 6 months after the initial gross hematuria. Autopsy was performed, and urothelial carcinoma was found in the right ureter as the primary lesion. The ureteral tumor infiltrated to the right kidney, right adrenal gland, liver, duodenum, and pancreas with undifferentiation. Undifferentiated tumor cells were also found in distant metastatic lesion including the abdominal lymph nodes, left adrenal gland, liver, lung, pleura, and peritoneum.