Metastasis from small-cell lung cancer to the colon is very rare. A 74-year-old man without respiratory or abdominal symptoms underwent a follow-up lower gastrointestinal endoscopy after a polypectomy. He was diagnosed with a 5 mm IIa non-hyperplastic polyp in the cecum and underwent a cold snare polypectomy. The histopathological findings confirmed the diagnosis of small cell carcinoma. The tumor was positive in the deep margins of the submucosal layer. Subsequent systemic examination revealed a mass in the lower lobe of the left lung. Thus, the tumor in the cecum was determined to be a colorectal metastasis from primary small-cell carcinoma of the lung. Metastasis to the colon was diagnosed as small-cell lung cancer based on local positivity for thyroid transcription factor-1 and morphologic and immunochemical features. To our best knowledge, this is the first report of colon metastasis from small cell carcinoma identified by endoscopic treatment.