A 52-year-old Japanese woman was diagnosed with primary follicular lymphoma of the duodenum that was curatively resected by pancreatoduodenectomy. She remained in complete remission until 11 years after the surgery, when multiple enlarged intra-abdominal lymph nodes were demonstrated by computed tomography scans and positron emission tomography scans. Two years later, jejunal lesions were detected by endoscopy, and biopsy samples confirmed a recurrence of follicular lymphoma. This case indicates that primary gastrointestinal follicular lymphoma has a potential of relapse after an extended period of time, and thus patients must be followed up for over 10 years after complete remission.