Background/aim: Obstructive sleep apnea syndrome (OSAS) is a disease characterized by repeated hypoxia attacks during sleep. The effect of hypoxia on the central nervous system is a well-known entity. In this study we aimed to investigate the effect of OSAS on the central auditory system. Materials and methods: Twenty-one OSAS patients diagnosed by polysomnography (PSG) and 10 control subjects were included in the study. After a thorough otorhinolaryngology examination, all subjects underwent pure tone audiometry (250 to 8000 Hz frequency). The subjects with normal otoscopic examination and hearing threshold were included in the study. All participants underwent speech discrimination analyses and auditory time processing and sequencing tests, i.e. frequency pattern test (FPT) and duration pattern test (DPT). Results: Although hearing was normal in the OSAS patients, significant loss was observed in the speech discrimination rates compared to the control group (P < 0.05). Significant disruption was also detected in the FPT and SPT in the OSAS patients (P < 0.05). Conclusion: Repeated hypoxic episodes in OSAS resulted in statistically significant impairments in the central auditory pathways, even if the hearing threshold was within normal limits.