We report the case of a patient with an optic neuropathy induced by neurotoxicity in the setting of methylmalonic acidemia. The patient responded with a significant and long-term improvement in visual acuity, perimetry, and chromatic function after a neuroprotective treatment with vitamin E and coenzyme Q10 was started. Coenzyme Q10 levels had been proven to be normal before starting treatment. This case report is particularly important because it describes a possible treatment for optic neuropathy in methylmalonic patients. Although the response might be, in part, specific to the individual, it suggests the existence of a cause-effect relationship between the treatment undergone by our patient and the improvement in her visual acuity. To date, no other treatments with beneficial effects have been reported for the few optic neuropathies caused by methylmalonic acidemia. Further studies should determine the applicability of coenzyme Q10 and vitamin E for the treatment of optic neuropathies in methylmalonic acidemia.