Sarcoid manifesting as an optic nerve tumor without evidence of systemic disease is uncommon. Throughout a 2-year period, a 22-year-old white woman had progressive monocular loss of vision to the level of no light perception. Optic atrophy but no uveitis was noted in the affected eye. Magnetic resonance imaging revealed thickening and enhancement of the apical optic nerve, with "tram-tracking." The presumptive diagnosis was optic nerve sheath meningioma; however, a biopsy specimen from the optic nerve revealed sarcoid. Extensive postoperative investigations revealed no systemic sarcoidosis. To our knowledge, 17 cases similar to ours, with the diagnosis proved by optic nerve biopsy, have been previously reported in the English-language literature. Most of these were mistaken preoperatively for optic nerve sheath meningioma. None of the patients had evidence of systemic sarcoidosis on initial postoperative testing. Neuroimaging, serum level of angiotensin-converting enzyme, and clinical characteristics such as age, race, sex, and optochoroidal collaterals do not distinguish optic nerve sheath meningioma from sarcoid of the optic nerve. In the absence of uveitis or systemic involvement, optic nerve sarcoid manifesting as an orbital tumor is virtually impossible to diagnose without results of biopsy.