Plasmacytomas of the urethra are extremely rare neoplasias; they may occur as isolated tumors or concomitantly with generalized multiple myeloma. Herein, we describe the clinical presentation and characteristics of a patient with primary plasmacytoma of the urethra. A 51-year-old man presented with terminal hematuria and a palpable penile mass. Magnetic resonance urethrography revealed a 3-cm long stenotic segment along which the urethral mucosa was found to be irregular. On urethroscopy, papillary mucosal projections extending to the presphincteric area were noted. Lesions were found to be composed primarily of neoplastic plasma cells capable of producing mainly lambda light chain. Upon diagnosis, the patient received external beam radiation therapy targeting the pelvic region. The lesion diminished in size progressively during the treatment course. He was disease-free after 6 months. Although it is a relatively rare disease, primary urethral plasmacystoma should be considered in the differential diagnosis of urethral tumors and radiation therapy should be an integral part of the treatment strategy.