Malignant optic nerve glioma (MONG) is a rare but uniformly fatal disease that remains poorly understood. We describe a notable case of this rare disease occurring in the optic chiasm. Normal brain imaging and normal ophthalmic examination two years prior to diagnosis provide evidence for de novo genesis of MONG in our patient. Early response to steroids highlights the degree to which MONG can initially mimic inflammatory optic neuropathies and chiasmal syndromes. Our case also demonstrates a poor outcome with MONG even with current advanced therapy for glioblastoma including radiotherapy plus concomitant and adjuvant temozolomide (the EORTC/NCIC regimen) and bevacizumab.