We report a rare case of sarcomatoid carcinoma of the urinary bladder which showed both of biphasic and monophasic phenotypes through its clinical course. A 64 year-old man presented with gross hematuria and interrupted voiding. Radiological examination demonstrated a pedunculated tumor in the bladder with no distant metastases. Pathological diagnosis of transurethral resection revealed biphasic sarcomatoid carcinoma, pT1, composed of squamous cell carcinoma component and spindle cell component. The disease repeated local recurrences and partial and total cystectomies were performed, respectively. The recurrent tumors were monophasic sarcomatoid carcinoma purely composed of spindle cell component. The patient died of local and metastatic disease 13 months after the diagnosis. We consider that sarcomatoid carcinoma should be resected radically at the initial surgical treatment because of aggressive potential of spindle cell component. To our knowledge, this is the first case in which biphasic sarcomatoid carcinoma of the bladder recurred as monophasic tumor. The pathological study and management of this neoplasm are discussed, and the literature is reviewed.