Skull base plasmacytomas are rare and difficult to differentiate clinically and radiologically from other tumors of the head and neck. Because of the risk of progression to multiple myeloma, early diagnosis is essential. We report the case of a 65-year-old woman who presented with left-sided conductive hearing loss and an external auditory canal mass. The tumor was removed along with much of the tympanic membrane, and it was found to be a plasmacytoma. The patient was subsequently diagnosed with multiple myeloma and treated with chemoradiation before being lost to follow-up.