A 22-year-old woman who was referred to our hospital presented with a complaint of urinary incontinence since childhood. Abdominal contrast-enhanced computed tomography revealed complete duplication of the left ureter. In addition, the upper half of the left kidney showed poor contrast, accompanied by signs of hydronephrosis. Magnetic resonance urography failed to show an opening between the upper half of the left kidney and the ectopic ureter. Cystoscopy revealed two normally positioned ureteral orifices. After intravenous injection of indigo carmine, however, the dye became evident in the vagina. Thus, she was diagnosed to have urinary incontinence due to complete duplication of the left ureter and an ectopic ureteral opening into the vagina. Transcatheter arterial embolization of the upper half of the kidney, the origin of the ectopic ureter, immediately relieved the patient of urinary incontinence. At the 6-month follow-up, the patient had experienced no recurrence or complications.