Solitary extramedullary plasmacytoma (EMP) of the rectum is an exceedingly rare entity. We report the fourth case of solitary EMP of the rectum and the first one treated by endoscopic polypectomy and radiotherapy. The patient showed no signs of local recurrence or dissemination of the disease after a 12-month follow-up. This case report is presented along with a review of the literature dealing with solitary plasmacytomas of the rectum.