A 66-year-old man, with a history of gastric signet ring cell carcinoma, was admitted due to intermittent dull pain in the left lower abdomen for 3 months. Left ureteral obstruction with suspicious tumor encasement and hydronephrosis was found on imaging studies. Endoscopic ureteral biopsy revealed infiltrating high-grade urothelial carcinoma. As a result, he underwent left nephroureterectomy and bladder cuff excision. Unexpectedly, metastatic carcinoma of the left ureter from the stomach was the final diagnosis after comparison of the permanent sections of the two specimens. Unfortunately, acute disseminated intravascular coagulation developed and the patient died of disease complications 16 days after the operation, even with intensive care. The details of this rare condition are reported herein with a review of the medical literature.