We report a case of obstructive ileitis (OI) secondary to colon cancer. A 62-year-old man was hospitalized for abdominal pain and a feeling of fullness. Examinations revealed a mechanical ileus caused by an obstructing carcinomatous lesion of the cecum. He underwent laparotomy on the tenth hospital day, and a right hemicolectomy was carried out with resection of the distended and edematous ileum. The histopathologic diagnosis was adenocarcinoma in the cecum involving the ileocecal valve and nonspecific inflammatory change of the ileum, with mucosal necrosis and neutrophilic infiltration involving the subserosal layer. His postoperative course was uneventful. OI does not always show similar histological features to obstructive colitis; however, they are both important types of obstructing lesions, and their possibility must be kept in mind during colorectal cancer surgery.