Sarcoidosis is a systemic, idiopathic granulomatous disorder with occasionally surprising clinical presentations. A primary involvement of the optic nerve is particularly important due to visual prognosis. We report here a patient with occult sarcoidosis who presented to us with progressive visual loss as the first and primary manifestation of the disease. The patient underwent surgery for histopathological diagnosis and decompression of the optic nerve. This case demonstrated that sarcoidosis should be considered in the differential diagnosis of any lesion involving the optic nerve.