We experienced a case of plasmacytoid urothelial carcinoma of the bladder. A 79-year-old man was referred with urinary frequency. Computed Tomography, Magnetic Resonance Imaging and ultra-sonography of the abdomen showed a diffuse and invasive mass occupying most of the bladder. Cystoscopy showed mostly non papillary tumor in the bladder, which was resected. Pathological examination of the specimen showed a diffuse monotonous cellular infiltration that invaded the lamina propria and the muscularis propria. He received radical cystectomy, and two cycles of systemic chemotherapy were performed with methotrexate, etoposide, vinblastine, and cisplatin, due to a lymphnode metastasis (pT3a, pN1, M0). He was disease free for 11 months. The tumor cells were medium-sized, round with eosinophilic cytoplasm and eccentric nuclei, producing a plasmacytoid appearance. Immunohistochemical studies were positive for epithelial markers and negative for lymphoid markers. So, we could diagnose as plasmacytoid urothelial carcinoma. This is a rare tumor. This case is the 30th case in the English literature.