Objective　To explore the clinical characteristics of clinically isolated syndrome (CIS). Method　The clinical data of visual and hearing impairment caused by CIS in a child were retrospectively analyzed. Results　A boy aged 5 years and 7 months visited the clinic due to poor eyesight and no abnormality was found in physical examination. His visual acuity of the right eye was 0.15, and the left eye was 0.15. Visual evoked potential showed delayed P100 peak and decreased amplitude in both right and left eyes. Brainstem auditory evoked potential and Distortion Product Otoacoustic Emissions (DPOAE) testing indicated that all the frequencies did not pass in the right ear; the frequencies except 4 kHz and 8 kHz did not pass in the left ear. TEOAE showed no frequencies passed in two ears. Neither electroencephalogram nor intelligence test (WPPSI) was abnormal. MRI examination of head and orbit suggested demyelination. These findings are consistent with the CIS diagnostic criteria for "A focal or multifocal clinical central nervous system event presumably associated with inflammatory demyelination". Conclusion　CIS can cause visual and hearing impairments.