A 41-year-old woman was diagnosed with duodenal follicular lymphoma. She had no other lesions and was assigned to a "watch and wait" policy. Swelling of the inguinal lymph nodes appeared 45 months later, and rituximab monotherapy resulted in complete remission. However, follicular lymphoma recurred in the stomach, rectum and mesenteric and external iliac lymph nodes 81 months after the therapy. The patient received rituximab monotherapy again and has remained in complete remission in the fifteenth year after the initial diagnosis. This case suggests the usefulness of rituximab monotherapy in the long-term management of intestinal follicular lymphoma.