Leigh syndrome or subacute necrotizing encephalomyelopathy is a rare, rapidly progressive neurodegenerative disorder. In general, symptoms such as shortness of breath and decreased cardiac function usually occur within 1 year of life. It is a serious disease with a mortality rate of 75% in 2–3 years. The cause of Leigh syndrome is DNA mutation. Approximately 75% of patients have nuclear DNA mutations while 25% have mitochondrial DNA mutations. Clinical symptoms vary depending on the affected brain area. Neuroimaging plays an important role in diagnosing patients with Leigh syndrome. Late-onset Leigh syndrome is rarer and progresses more slowly compared to the classic form. Here, we report a case of late-onset Leigh's syndrome mimicking Wernicke's encephalopathy.