Primary neuroendocrine tumors of the upper urinary tract are extremely rare. We report a case of de novo small cell carcinoma of the ureter that presented masquerading as a distal ureteral stone. A 55-year-old lady presented to our clinic with 1 month history of right lower back pain and hematuria. Her history was notable for stage 1B mixed clear cell-endometroid cancer of the uterus status post radical abdominal hysterectomy with adjuvant radiotherapy, 7 years before the current episode. The patient had no evidence of recurrence. Initial noncontrast imaging suggested a 2.5 mm calculus in the distal right ureter and hydronephrosis; however, ureteroscopy revealed a large fleshy mass at the location. Histopathologic evaluation demonstrated the lesion to be primary small cell carcinoma of the ureter, without evidence of it being a derivative of the prior gynecologic malignancy. Metastatic work-up revealed high burden retroperitoneal adenopathy. The patient was started on Cisplatin-based neoadjuvant chemotherapy with plan for nephroureterectomy in the future. At 3 months follow-up, the patient was doing well with significant shrinkage of retroperitoneal adenopathy and no evidence of disease progression.