Primary malignant lymphoma located in the duodenum is a rarity. A case of primary lymphoma of the duodenum in a 27-year-old man, in which the 2 discrete masses of duodenal bulb and the second portion with pancreatic head invasion was found, is reported here. Immunohistochemical evaluation of the present case showed that lymphoma cells expressed the T-cell markers MT1 and UCHL1. Treatment consisted of pancreaticoduodenectomy followed by antineoplastic chemotherapy.