Primary gastrointestinal follicular lymphoma is a rare disease. Follicular lymphoma does not cause any typical symptoms, although it usually shows the presence of multiple white granules on endoscopy. Few patients with follicular lymphoma present with the initial symptom of jaundice, which is usually associated with follicular lymphomas located in the papilla of Vater. Herein, we present the first case of a duodenal follicular lymphoma that presented with obstructive jaundice despite not being in the ampulla, and it did not demonstrate the typical endoscopic findings of multiple white granules. A 72-year-old Japanese man with jaundice was referred to our hospital. Imaging revealed a hypo vascular lesion extending into the second part of the duodenum and the pancreatic head, and the common bile duct was dilated upstream of the lesion. Biopsy of the lesion was negative for malignancy. Finally, we suspected the lesion as a pancreatic adenosquamous carcinoma, and not a typical pancreatic ductal carcinoma, because the lesion showed no pancreatic duct dilation and had a partially hyperechoic part within. Therefore, we performed pancreaticoduodenectomy. The final diagnosis was a duodenal follicular lymphoma. The findings of this case may assist in distinguishing between atypical follicular lymphoma and jaundice from pancreatic cancer.