A 59-year-old man was referred to our hospital complaining of asymptomatic gross hematuria. Cystoscopy revealed a papillary tumor 8 cm in diameter filling the bladder. The patient underwent transurethral resection of the bladder tumor. The pathological findings revealed the sarcomatoid variant of urothelial carcinoma with a heterologous osteosarcomatous element. He had no metastasis according to our imaging analyses; thus, we planned radical cystectomy after two courses of neoadjuvant chemotherapy (gemcitabine and cisplatin). Following chemotherapy, enlarged pelvic lymph nodes were noted, and extremely aggressive local progression of the bladder tumor was confirmed. The patient ultimately died 6 months after his initial visit to our hospital.