A 30-year-old young previously healthy man presented to our hospital with middle and upper abdominal discomfort. Abdominal computerized tomography (CT) showed no significant abnormalities. White light endoscopy showed the local mucosa in the descending part of the duodenum had granuloid uplift, some of which were fused into pieces with red color, and some other areas showed fading tone. Magnifying endoscopy with indigo-carmine staining and narrow-band imaging showed a finger-like, loose villous structure with irregular microvessels on the surface. Pathological examination of biopsy specimens showed that lymphocytes were diffused and dispersed in the mucosa with relatively simple morphology, no lymphoid follicles were observed, and local compression was obvious. Immunohistochemical staining revealed a lymphoid population highly positive for CD20 and CD10. These results were consistent with duodenal-type follicular lymphoma (D-FL).