We report the first case of primary extramedullary plasmacytoma of the liver. The tumor was situated in segment VIII of the liver without extrahepatic extension. Histologically, the tumor was composed of sheets of mature plasma cells with slight atypia in association with proplasmacytes invading the hepatic parenchyma. Neither plasmoblasts nor lymphoplasmacytes were present. Immunohistochemistry demonstrated monoclonal IgG and kappa light-chain expression. In situ hybridization confirmed the monotypic expression of kappa light-chain mRNA. Bone marrow examination revealed no abnormality. After surgery, the IgG kappa spike detected in preoperative plasma samples decreased. The patient is disease free 31 months postoperatively.