Extramedullary plasmacytomas are rare plasma cell tumors of the soft tissue that predominantly occur in the head and neck. They are most commonly seen in the upper respiratory passages and oral cavity. There have been only a few reports in the world literature of plasmacytomas occurring within the temporal bone. This report presents a case of plasmacytoma of the middle ear and mastoid that presented as a middle ear mass. Work-ups for systemic dissemination and multiple myeloma were negative, classifying this as a localized extramedullary plasmacytoma. This is the first report in the English literature of this malignant tumor occurring as an isolated lesion within the middle ear and mastoid. The patient was treated with surgical debulking and radiotherapy with complete resolution of the tumor. Although extremely rare, plasmacytoma should to be included in the differential for soft tissue tumors of the middle ear and mastoid.