The aim of the study is to present an atypical case of late-onset X-linked retinoschisis. We present a case of a 37 year-old male patient with a few months' history of visual impairment. A clinical exam with optical coherence tomography and flash electroretinography (flash-ERG) was performed and the patient was diagnosed with X-linked retinoschisis. Genetic testing of the patient's family confirmed the disease and p.Arg197Cys mutation of RS1 gene was identified. In conclusion, optical coherence tomography and flash electroretinography enabled a proper diagnosis of X-linked retinoschisis in a patient with symptoms manifesting in the fourth decade of life. Genetic testing revealed male sufferers and female carriers among his family members.