This case report describes clinical signs, computed tomography and laboratory diagnostic findings of an extramural ectopic ureter in a ferret. A 1-year-old, female domestic ferret weighing 900 g was referred to LLU Veterinary Hospital with a history of permanent urinary incontinence. Previously performed blood tests and abdominal radiographs were without significant changes. Abdominal ultrasound did not reveal any abnormality. Computed tomography (CT) post-contrast images showed a contrast-enhanced left ureter opening in the vagina. The CT confirmed the diagnosis of the left extramural ectopic ureter and surgical treatment was recommended. Two weeks after left-sided nephroureterectomy, incontinence still was noted but urine leakage was decreased. The outlined results will be useful for all veterinary practitioners and will update their knowledge on urinary incontinence disorders in domestic ferrets.