We report the radiologic findings from three cases of solitary plasmacytoma (SP) of the sacrum. Common findings included lytic changes on computed tomography (CT) and relatively low signal intensity on T2-weighted magnetic resonance (MR) images, with intense enhancement after contrast administration. All cases showed infiltrating and slightly expansive growth, but the sacral structure was generally maintained. These radiologic findings may be of utility when generating a differential diagnosis of a solitary sacral tumor.