To report a case of an optic nerve sheath meningioma located at the optic canal area mimicking the progression of a glaucomatous axonal damage. A 60-year-old female patient developed progressive visual field loss and enlargement of the optic disc cup in the left eye while in treatment for primary open-angle glaucoma. Because of the rapid progression of axonal loss, the asymmetry of the visual field defect and the fact that intraocular pressure had been under control, a compressive optic neuropathy was suspected. A computerized tomography scan of the orbit was normal but a high-resolution magnetic resonance imaging demonstrated an optic nerve sheath meningioma located at the optic canal area. Compressive lesions of the anterior visual pathways are uncommon causes of optic disc cupping but should be considered in patients suspected of or undergoing treatment for glaucoma that present with atypical progression of visual loss.