Sudden onset sensorineural hearing loss is an emergency condition in otorhinolaryngology. Despite its common occurrence, the investigation and treatment of this condition are still controversial. Auditory brainstem response is one of hearing assessment tools used in sudden onset sensorineural hearing loss. However, its findings may be false positive at early stages of the disorder, leading to unnecessary investigations and treatments. We report two cases of idiopathic sudden onset sensorineural hearing loss, which manifested in abnormal auditory brainstem response during the acute phase of illness. However, a complete recovery of auditory brainstem response was observed after treatment completion. Therefore, we suggest that auditory brainstem response should be performed reasonably, especially during the acute phase of sudden onset sensorineural hearing loss.