Congenital hypothyroidism (CH) has a considerably high prevalence in our country, and without early treatment, it would lead to irreversible sequelae like hearing impairment. This study was aimed to investigate the prevalence of hearing loss in children with CH in comparison with healthy children. Background: This case-control study was conducted in two groups of children; the case group consisted of 94 children with CH aged more than 4 months under follow up in Isfahan endocrine research center; the control group included 450 healthy infants underwent routine neonatal hearing screening in a private hospital. First, Otto Acoustic Emission (OAE) test was performed, and in the case of being abnormal, then auditory brain stem response (ABR) test was conducted. Children with abnormal ABR were considered to have hearing impairment. Methods: The prevalence of hearing impairment was not significantly different between children with CH and controls (3.2% vs. 0.2%, respectively; p>0.05). The mean age of beginning the treatment for CH was not significantly different between children with or without hearing impairment (13.6±8.3 vs. 16.4±8.05 days, respectively; p>0.05).The mean T4 and TSH was not significantly different between children with CH with and without hearing impairment (5.6±4.2 mg/dl and 133.7±80.3 MIU/l vs. 6.2±3.7 mg/dl and 116.5±92.1 MIU/l, respectively; p>0.05). Findings: We did not document any difference in the prevalence of hearing impairment in children with CH and controls; this finding might be because of limited number of subjects studied and the short duration of follow up. There was no difference neither between the age of beginning the treatment for CH and hearing impairment, nor between the mean T4 and TSH at birth and hearing impairment. Hearing loss has no relationship with age at treatment onset and primary T4 and TSH level at diagnoses. Conclusion: Congenital hypothyroidism, hearing impairment, audiometry Key words