An eight-year-old male entire boxer dog was presented by the owner with a four-week history of haematuria. Abdominal ultrasound identified a moderately dilated left ureter from immediately distal to the renal pelvis to a focal stenosis at the level of L5. Intravenous urography showed a diffusely tortuous proximal left ureter with irregular contrast borders and focal stenosis distally. Left ureteronephrectomy was performed and histology of the left ureter revealed a primary ureteral urothelial (transitional cell) carcinoma infiltrating the ureteral wall. This is the first imaging description of a primary ureteral urothelial carcinoma and only the second description of a primary ureteral urothelial carcinoma in veterinary literature.