Sarcomatoid carcinoma is a rare tumor of the urinary bladder accounting for less than 0.5% of all primary urinary bladder tumors. Since the patients were presented with large tumor with extended stages, outcome was found to be poor. In order to improve local control, adjuvant local treatment may be practical. We report a rare case with sarcomatoid carcinoma of the urinary bladder diagnosed with immunuhistochemical (IHC) study and treated with 3D-conformal radiotherapy (3DCRT) post-operatively. A 55-year old female patient complained about painless hematuria for 2 months. Computed tomography of the pelvic region revealed tumor and wall thickening at the left posterolateral side of the bladder. Total cystectomy with lymph node dissection and total abdominal hysterectomy and bilateral salphingo-oopherectomy was performed and histopathological and immunohistochemical findings strongly correlate with sarcomatoid carcinoma. The patient was treated with 3D conformal radiotherapy (3DCRT) with a total dose of 59.4 Gy with 1.8 Gy fractional daily doses. Patient was alive without any local recurrence and distant metastasis 10 months after surgery.