Pseudopolyp is a common association of ulcerative colitis but may also occur in Crohn's disease, ischemic colitis and infective colitis. Pseudopolyps are results of the repair process, representing islands of granulation tissue surrounded by mucosa with ulceation. When a pseudopolyp is larger than 1.5 cm, it is often called a "giant pseudopolyp". Such lesions of inflammatory origin are often confused with polypoid carcinoma or infiltrating submucosal malignancy. We report a case of asymptomatic Crohn's disease as giant pseudopolyposis mimicking malignancy on sigmoid colon, with a review of relevant literatures.