Gastrointestinal ganglioneuroma is a rare benign neoplasm, composed of ganglion cells, nerve fibers, and supporting cells. Ganglioneuromas are presented as isolated polypoid ganglioneuroma, ganglioneuromatous polyposis, and diffuse ganglioneuromas. We have experienced a case of an isolated ganglioneuromatous polyp in the rectum. The patient was a 58-year-old female who had experienced low abdominal discomfort and tenesmus for 6 to 7 months. Colonoscopic examination revealed a polypoid tumor in the rectum. Microscopically, the tumor showed cystic glands, expanded lamina propria, and smooth surface epithelium. Many proliferated ganglion cells with nerve fibers were evident in the lamina propria which was extended to the submucosa.