Colonic lipomas are a rare type of gastrointestinal benign tumor. Those that are <2 cm are generally asymptomatic and do not require any treatment. However, those that are >2 cm may be symptomatic, resulting in abdominal pain, changes in bowel habits, intestinal obstruction and rectal bleeding. A 39-year-old male patient presented with a mass prolapse through the anal canal, which was causing anal pain and rectal bleeding. The patient was admitted to hospital via the emergency services and directed to the Department of General Surgery with the preliminary diagnosis of a rectal prolapse. A pedunculated polyp (size, 10x8x7.5 cm) was detected at the 35th cm of the anal canal. Due to the large size of the polyp, an endoscopic polypectomy could not be performed. Therefore, the prolapsed lipoma was excised externally and the patient was discharged on the first postoperative day on which no complications were experienced. A colonic lipoma must be considered during the differential diagnosis of anorectal diseases, such as hemorrhoids and rectal prolapses. Local excision, hemicolectomy, and segmental and external resection should be considered in addition to an endoscopic polypectomy for the diagnosis and treatment of colonic lipomas.