Neurofibromas are benign, slow-growing nerve sheath tumors of the peripheral nervous system, arising from Schwann cells, and classically associated with neurofibromatosis type 1 (Nf1, von Recklinghausen's disease). They occur rarely in the gastrointestinal tract as isolated neoplasms, outside the classical clinical feature of neurofibromatosis. We herein present an isolated colonic neurofibroma without any systemic signs of neurofibromatosis. A 59-year-old female came to our hospital for constipation. On physical examination, general appearance showed no definite skin lesions. A subepithelial tumor measuring 0.8 cm was detected at the distal descending colon on colonoscopy. The lesion was removed completely by endoscopic resection. Microscopic examination showed proliferation of spindle cells in the mucosa and infiltration of inflammatory cells. Immunohistochemical staining was positive for S-100 protein. The above morphological and immunohistochemical characteristics were consistent with a diagnosis of a solitary neurofibroma of the sigmoid colon.