a b s t r a c tStroke occurs due to the interruption of blood flow to the brain and it is divided into ischemic and hemorrhagic. In the ischemic strokes, while the most commonly affected vessel is median cerebral artery (MCA), it is particularly affected bilateral posterior cerebral artery (PCA) is very rare condition. In this study, a case of sudden loss of vision and bilateral occipital infarct associated with bilateral vertebral system pathology and methylene tetrahydrofolate reductase (MTHFR) gene mutation were reported. A 62-year-old man was admitted with sudden loss of vision complaint starting 10 h before applying to emergency department. The patient was oriented and cooperative. On neurological examination, there was complete loss of vision in the right eye and only a response to light in the left eye. On the brain computerized tomography (CT), ischemic lesions were observed in the bilateral occipital areas and on magnetic resonance imaging (MRI), there were foci showing diffusion limitation in cortico-subcortical areas of bilateral parieto-occipital region. On the detailed examination at the clinic, MTHFR (a1298c) gene mutation was detected. Bilateral occipital infarction is rare and its diagnosis can be difficult because of its atypical symptoms. Therefore, occipital infarction should be suspected when the only sign is isolated vision loss in patients with risk factor for thromboembolism in their history and detailed visualneurological examination of these patients should be performed.