We present a case of a 78-year-old man who presented at the Otorhinolaryngology Department with fullness of the ear, progressive hearing loss, and a rapidly growing polypoid mass in the external auditory canal (EAC). In 2009, the patient was diagnosed with multiple myeloma and amyloidosis and was in follow-up. A computed tomography (CT) scan requested by the hematology department revealed an oval lesion with soft tissue attenuation occupying the EAC and the tympanic cavity. The mass had eroded the walls of the EAC, incus, hammer, and tegmen timpani, and had invaded the middle cranial fossa preserving the inner ear structures. An incisional biopsy was performed, which revealed a histopathological diagnosis of a secondary extramedullary plasmacytoma. The plasmacytoma is a rare malignant tumor, originated proliferation, and irreversibly independent of plasma cells. It may appear as a circumscribed mass or diffused infiltration that accumulates in the bone marrow or in extramedullary sites and is usually found in multiple myeloma patients. Plasmocytoma extramedulare is commonly found in the head and neck, especially in the paranasal sinuses, nasopharynx, and tonsillar region. Reports of cases with middle ear plasmocytomas are rare. Many of these plasmocytomas manifest as solitary plasmocytomas or as part of widespread bone diseases. Treatment includes radiation therapy, local surgical control, or a combination of the 2 treatment methods. The prognosis of this injury is uncertain, and its relationship with disease activity requires further studies. The objective of this report is to present a rare case of plasmacytoma of the middle ear associated with multiple myeloma and discuss the diagnostic challenges and possible treatment methods of the injury along with its prognosis.