Intracranial infiltration is a rare complication of multiple myeloma (MM), which is usually seen in advanced stage. Here, we report a 47-year-old woman with only cavernous sinus syndrome as first manifestation. Brain MR revealed cavernous sinus masses, leptomeningeal nodules, and osseous erosion, which were considered metastases. F-FDG PET/CT, which was further performed to identify potential primary lesions, showed increased uptake not only in cavernous sinus and leptomeninges but also in diffuse bone lesions, hepatic nodules, lymph nodes, subcutaneous nodules, and bilateral ovarian masses. Multiple myeloma with intracranial involvement was confirmed by biopsy and cerebrospinal fluid examination.