We describe our encounter with a 39-year-old man who exhibited acute painless visual loss and progressive gait disturbance. He had tendinous xanthoma and several neuroophthalmological findings indicative of optic neuropathy in the right eye, including afferent pupillary defect, cecocentral scotoma, and optic disc swelling. Neurological examination showed cerebellar ataxia and pyramidal weakness. Brain magnetic resonance imaging revealed bilateral swelling in the optic nerves with gadolinium-enhancement suggesting optic neuritis, an enlarged fourth ventricle, atrophy of the cerebellum, and hyperintensities in the bilateral dentate nuclei. The patient was diagnosed with cerebrotendinous xanthomatosis (CTX) based on an elevated serum cholestanol level and a homozygous missense mutation in CYP27A1. CTX is a genetic lipid storage disease caused by dysfunction of the mitochondrial enzyme sterol 27-hydroxylase. With respect to ophthalmological manifestations, juvenile cataracts and optic neuropathy are common findings in patients with CTX, but there have been no reports of optic neuropathy with features suggestive of optic neuritis. Thus, this case illustrates that clinicians should consider a diagnosis of CTX in patients with cardinal features of CTX even if the patients show signs indicative of optic neuritis.