Malignant optic nerve glioma is a rare but uniformly fatal disease that remains poorly understood. The authors describe a notable case of this rare disease occurring in the optic chiasm. Normal brain imaging and normal ophthalmic examination 2 years prior to diagnosis provide evidence for de novo genesis of malignant optic nerve glioma in their patient. The patient’s early response to steroids highlights the degree to which malignant optic nerve glioma can initially mimic inflammatory optic neuropathies and chiasmal syndromes. This case also demonstrates a poor outcome for malignant optic nerve glioma even with current advanced therapy for glioblastoma using radiotherapy plus concomitant and adjuvant temozolomide and bevacizumab.