A 57-year-old male with a 1-year history of recurrent oral ulceration and papulopustular lesions presented with acute visual loss in his left eye. He had an oedematous disc without any signs of uveitis. Laboratory work-up regarding infectious diseases was negative. The patient was diagnosed with acute optic neuropathy secondary to Behçet's disease. Systemic steroid and colchicine treatments were started but his vision did not improve. Isolated optic neuropathy is rare in Behçet's disease and early treatment with high-dose steroids may not be successful in some cases.