Plasmacytomas rarely affect the skull base and may be found as an isolated lesion or as a part of multiple myeloma. The typical feature of plasmacytomas is aggressive bone destruction in the skull. It is often confused with the chordoma of the clivus. The most common location for skull-base plasmacytomas is the nasopharynx. The most commonly affected cranial nerve in clivus tumors is the abducens nerve. In our 64-year-old male case, a plasmacytoma was detected in the clivus. There was ptosis and decreased vision due to optic nerve and oculomotor nerve involvement due to the plasmacytoma. Radiotherapy was applied for the treatment.