Plasmacytoma is a rare plasma cell tumour that arises from plasma cells. The tumour accounts for about 3 - 5% of all plasma cell malignancies and most often affects the head and neck, but may also occur in the gastrointestinal tract. To our knowledge, mesenteric plasmacytoma has not been described previously. We describe the presentation and management of a case of mesenteric plasmacytoma presenting as an abdominal mass in a 69-year-old HIV-positive man.