Malignant plasma cells in multiple myeloma are predominantly confined to the medullary space of the skeletal system, therefore the disease course will be dominated by signs and symptoms related to bone marrow infiltration and destructive bone lesions with their consequences as well as abnormal protein production. Visceral extramedullary plasmacytoma involving the gastrointestinal system and particularly the duodenum is a rare manifestation of the disease. We report a case of duodenal extramedullary plasmacytoma presenting with gastric outlet obstruction and painless jaundice, in a patient treated for multiple myeloma. Diagnosis was first suggested on imaging, and proved by endoscopic biopsy. The duodenal mass resolved following chemotherapy.