We report a case of urinary bladder carcinosarcoma with simultaneous testicular seminoma. A 60-year-old male presented with painless gross hematuria and a left testicular mass. The bladder tumor was deeply infiltrating muscular tissue and had histologic features of both carcinoma and sarcoma. Testicular tumor was diagnosed as classical seminoma. Radical cystectomy, pelvic and left-modified retroperitoneal lymphadenectomy were performed. The l lymph nodes did not show metastasis. At the 26 months follow-up, the patient is free of disease.