|Ganglioneuromas (GNs) in adults are uncommon clinical entities, especially in the colon. Patients with GNs without multiple endocrine neoplasia or neurofibromatosis-I are normally asymptomatic; however, GNs can present with abdominal pain, weight loss, bleeding, and anemia, depending on the size and location. Here, we present a case of solitary colonic GN treated with endoscopic mucosal resection. A 40-year-old Japanese outpatient with a positive fecal occult blood test visited our hospital. We performed diagnostic colonoscopy, which revealed a polyp of 15-mm diameter in the ascending colon. Electromagnetic resonance imaging was performed, and the histological examination revealed benign polypoid spindle-cell proliferation, ganglion cells, and thick nerve bundles, which was positive for S-100 protein immunoreactivity consistent with GN.