We report a case of a rare solitary ganglioneuroma occurring in the sigmoid colon of a 70-year-old woman. She experienced sudden onset of abdominal pain and loss of old blood from the gastrointestinal tract. A colonoscopy disclosed a pedunculate polyp in the sigmoid colon 20 cm from the anus, and a histopathologic examination revealed a polypoid mucosa with abundant ganglionic cells and nerve fibres.