We report a case of 53-year-old man with plasmacytoid transitional cell carcinoma of the urinary bladder, which may be confused with plasmacytoma. The patient initially presented with gross hematuria and dysuria for two months. Cystoscopy and radiologic studies revealed multiple intraluminal protruding masses on the urinary bladder invading perivesical fat tissue. After urinary cytologic examination and cystoscopic biopsy, radical cystectomy and pelvic lymph node dissections were done. Urine cytology showed single cells and poorly cohesive cells with round eccentric nuclei, bi-or multi-nucleation, indistinct nucleoli, coarse chromatin, and abundant basophilic cytoplasm within relatively clear background. The cytologic findings of tumor cells were similar to the plasma cells seen in plasmacytoma. The tumor of the bladder was composed of discohesive, individual cancer cells with diffuse pattern that simulated lymphoma or plasmacytoma. Immunohistochemical and electron microscopic studies clearly established the epithelial nature of the neoplasm. Recognition of this plasmacytoid type of transitional cell carcinoma of the urinary bladder can avoid the misdiagnosis.