Although hearing loss in newborns and infants is predominantly due to malformations and infections, there are other situations which may compromise hearing quality in later stages, including posterior-fossa arachnoid cysts (ACs). We report the case of an 8-year-old girl who presented with hearing loss linked to a pontocerebellar-angle AC which had been diagnosed and treated when she was 14 months old. The pathophysiology of this late AC complication is discussed. This case reminds us that a close follow-up with audiologic monitoring and/or brain stem auditory evoked response is necessary in children with posterior-fossa AC because modern neuroradiological imaging methods do not inform about cerebral and nerve functions, although they provide excellent morphological details of ACs and have improved the ease and accuracy of their early diagnosis. Therefore, surgery should be performed before complete hearing loss occurs; however, in hearing-impaired patients, it remains unclear which surgical treatment is most appropriate.