We report the case of a 41-year-old man who presented with progressive right-sided ear pressure, otalgia, hearing loss, tinnitus, and intermittent otorrhea. Computed tomography and magnetic resonance imaging detected a soft-tissue mass in the right mastoid with intracranial invasion and erosion through the tegmen tympani and mastoid cortex. Histopathologic examination was consistent with an inflammatory pseudotumor (plasma cell granuloma). These lesions rarely occur in the temporal bone. When they do, they are locally destructive and can erode bone and soft tissues. Aggressive surgery is recommended as a first-line treatment, with adjunctive steroid or radiotherapy reserved for residual or refractory disease. Our patient subsequently experienced multiple recurrences, and his treatment required all of these modalities. At the most recent follow-up, he was disease-free and doing well.