Multiple lymphomatous polyposis (MLP) is an uncommon type of primary non-Hodgkin gastrointestinal (GI) B-cell lymphoma characterized by the presence of multiple polyps along the GI tract. Malignant cells of MLP have mantle cell characteristics and thus are considered to be the counterpart of the mantle cell lymphoma (MCL) in the GI tract. Since 1961, no more than 70 well-documented cases have been published. We report the case of 53-year-old man diagnosed as having MLP. The patient presented with diffuse abdominal pain, chronic lower GI bleeding, peripheral lymphadenopathy, and weight loss. The lymphomatous polyps extended from the esophagus to the rectum, with bone marrow infiltration. Immunohistologic findings were characteristic of MCL. The patient was treated with a combined cyclophosphamide, vincristine, and prednisone chemotherapy regimen, resulting in a partial response.