OBJECTIVE To describe an uncommon case of malignant optic glioma and the challenges in its diagnosis. METHODS Case report with funduscopic, magnetic resonance imaging (MRI), and automated field test correlations. METHODS A 60-year-old man presented with a 1-week history of left optic disk swelling and optic neuropathy that was initially diagnosed as nonarteritic anterior ischemic optic neuropathy (NA-AION). RESULTS His clinical course deteriorated with progressive vision loss, acute orbital inflammation, and central retinal vein and artery occlusion, despite an improvement with a short course of steroids. MRI revealed enhancement of the left optic nerve, chiasm, and left optic tract. Initial optic nerve biopsy was negative and biopsy of optic tract confirmed a diagnosis of glioblastoma multiforme grade 4. The patient died 4 months after biopsy despite chemotherapy and radiotherapy. CONCLUSIONS The diagnoses of malignant optic glioma, anterior ischemic optic neuropathy, and optic neuritis have significant overlap of signs and symptoms. The authors report a case that demonstrates the difficulties in diagnosis, and propose additional presenting features of malignant optic glioma.