Optic perineuritis is an uncommon inflammatory disorder of the optic sheath that causes visual loss or eye pain. There are few case reports of optic perineuritis associated with granulomatosis with polyangiitis. Herein we report the case of a 37-year-old male with granulomatosis with polyangiitis and who presented with headache, blurred vision in the right eye, diplopia, and numbness in the right forehead. Brain magnetic resonance images (MRI) findings revealed hypertrophic pachymeningitis and refractory optic perineuritis. These were manageable only by means of weekly methotrexate and mycophenolate mofetil combination therapy but not with methotrexate, mycophenolate mofetil, intravenous cyclophosphamide, rituximab, azathioprine, or cyclosporine individually.