Accumulation of urine in the pleural space secondary to uroperitoneum with no disruption of the diaphragm appears to be a rare pathological condition. A 2 yr old male mixed-breed dog was referred with dyspnea and abdominal pain after a road traffic accident. Plain radiographs demonstrated pleural effusion and reduced serosal detail in the abdominal cavity that was compatible with fluid accumulation. Retrograde urethrography revealed a pelvic urethra rupture. Biochemical analysis of the pleural and abdominal fluid confirmed the diagnosis of urothorax and uroperitoneum. The dog underwent a prepubic urethrostomy and intensive care management. The dog was reported to be in good health after a follow up time of 10 mo. To the authors' knowledge, this is the first reported case of urothorax associated with uroperitoneum with no detectable defects of the diaphragm in a dog.