Skull base involvement of plasmacytoma is reported in a patient with light chain myeloma. A 39-year-old man was admitted after experiencing paresthesia on the left side of the face and left arm, intermittent diplopia, and hoarseness for 2 years. Cranial magnetic resonance imaging revealed a large midline mass extending from the middle and posterior skull base into the upper two cervical vertebrae. An extramedullary plasmacytoma associated with light chain multiple myeloma was diagnosed after biopsy of the mass and laboratory investigations. The imaging findings and clinical features associated with this rare site of extramedullary plasmacytoma involvement are reported.