We report a unique case of giant obstructing inflammatory polyposis associated with ulcerative colitis (UC). A 25-year-old Japanese man with an UC history of 2 years and 6 months was referred to our institution because of diarrhea and melena. His computed tomography scan showed marked dilation of the transverse and descending colon; therefore, we performed total colectomy. Macroscopic evaluation of the excised specimen indicated constricting lesions with giant polyposis in the transverse and descending colon. The polyposis consisted of narrow worm- or noodle-like polyps that bridged over the irregular ulcers. Histologic evaluation of the excised specimen indicated transmural inflammation with a thickened proper muscular layer overlaid with inflammatory polyposis. Based on these data, a diagnosis of giant inflammatory polyposis should be considered in patients who have had UC. Although giant inflammatory polyposis is considered benign, surgical treatment may be indicated to avoid serious complications.