A 14-year-old intact female, mixed dog was presented with hematuria and strangury. Mass in the abdominal cavity was seen on radiographs and ultrasound. On the cytological examination in the urethra, clusters of pleomorphic epithelial cell were found. Tissues of the urethra and the urinary bladder were obtained at the time laparotomy and determined the extent of the mass. Transitional cell carcinoma (TCC) of the urinary bladder was found in histopathologic characteristics. Urinary diversion after removal of a complete full section of the TCC in bladder wall was performed. Piroxicam, as a medical therapy for TCC, was orally administrated. Surgical operation and chemotherapy were selected with the goal of maintaining and improving quality of life.