Hyperplastic polyps are common large-bowel tumors, are frequently detected in middle- to old- aged people, and usually are minuscule lesions in the distal colon and rectum. Most hyperplastic polyps have no malignant potential, but recent studies suggest that some hyperplastic polyps can progress to colorectal cancers, possibly by the so-called serrated pathway. Hyperplastic polyposis is a rare syndrome characterized by multiple hyperplastic polyps, primarily in the proximal colon. Different from sporadic hyperplastic polyps, hyperplastic polyposis is alleged to have high potential for malignancy because patients with this syndrome may frequently have conventional adenomas, serrated adenomas, and adenocarcinomas. We report the case of a patient with hyperplastic polyposis, who had two synchronous colon cancers, as well as sessile serrated adenomas and tubular adenomas.