Osseous metaplasia within the gastrointestinal tract is rare and occurs in benign, premalignant, and malignant neoplasms. Here, we report the youngest case of an adenomatous polyp with the presence of ossification and a concomitant review of the literature with regard to ossification of colonic polyps. A 28-year-old man underwent colonoscopy for 8 months of rectal bleeding. A 4.5-cm pedunculated polyp was found in the descending colon and excised. Histological examination showed adenomatous change with an area of calcification and osteoid formation. Ossification of colonic polyps is mainly associated with the clinical symptom of bleeding and may warrant consideration as a high-risk feature.