A 48-year-old man was admitted to our hospital because of repeated episodes of epigastralgia. Endoscopy showed multiple whitish granules extending from the 2nd to 3rd portion of the duodenum. Biopsy specimens showed well circumscribed follicles with a monotonous population of predominantly small cleaved cells that were positive for CD20, CD10 and BCL2, but negative for CD5. A full staging study showed no abnormalities. The tumor was finally diagnosed according to the WHO classification as a stage I follicular lymphoma (FL), grade 1, of the duodenum and subsequently received irradiation to the involved area. After 3 years of followup, he is still in complete remission. Because FL arising in the duodenum has recently reported with increasing frequency, patients with multiple granules in the duodenum should be examined carefully.