Abstract: Plasmablastic lymphoma (PBL) is a rare subtype of diffuse large B-cell lymphoma, predominantly occurring in the oral cavity of human immunodeficiency virus-positive patients. It is clinically characterized by high aggressiveness and currently lacks effective treatment options. Gastrointestinal tract involvement in PBL is rare, with duodenal involvement being particularly uncommon. The authors report the ¹⁸F-fluorodeoxyglucose PET/CT imaging findings of a case of duodenal PBL, combining the patient's clinical features with a review of relevant literature, aiming to enhance nuclear medicine physicians' understanding of this disease.