Background: A hearing loss of at least 30 decibels over three successive frequencies in less than 72 hours is referred to as idiopathic sudden sensorineural hearing loss (ISSNHL). Auditory brainstem response may serve as a potential prognostic indication in patients with ISSNHL, according to several studies. Low serum thyroid hormone levels can contribute to hearing loss since they are strongly tied to the cochlea's proper functioning. Aim: To investigate the prognostic value of ABR and the association between its results and the thyroid hormone serum levels in ISSNHL patients. Methods: Observational prospective study was conducted on thirty patients with ISSNHL that occurred within the last 72 h with 30 dB hearing loss at three sequential frequencies. Pure tone audiometry, word discrimination scores, immittencemetry and auditory brain stem response were performed on the day of admission then again on the third day after admission and one month later. Thyroid hormone serum level were assessed after admission. Result: Hearing recovery was observed in 21 patients (70%). The absolute latencies of waves I, III, and V latencies were statistically significantly delayed in the affected ears compared with the unaffected ears. There was a statistically significant correlation between hearing outcome and wave I latency. Wave V latency was statistically significantly negatively correlated with free T4. Conclusion: Auditory brainstem response is an important prognostic factor in ISSNHL but caution should    be considered when adopting ABR testing without assessing thyroid hormone levels.