Several studies have reported that patients with essential tremor (ET) may also have mild cognitive impairment. Event-related potentials (ERPs) involve cognitive processes in the brain. No detailed investigation has been conducted into auditory ERPs (AERPs) to detect the subclinical cognitive dysfunction in patients with ET. Therefore, this study aimed to clarify the usefulness of AERPs in ET-related cognitive impairment. The AERPs were obtained by using an oddball paradigm in 27 patients with ET and 27 age-matched control subjects. The mean latency and amplitude of the ERPs were compared between the two groups. The correlation between disease duration and the mean values of all components of the potentials was assessed. The association between tremor severity and potentials was also evaluated. The patients with ET showed significant prolongation of all components of the ERP latencies at each electrode site. The N200 and P300 amplitudes were reduced in the ET group. Interestingly, the significant prolongation of N100 and N200 latencies correlated with disease duration, and N200 latencies appeared significantly longer in patients with severe tremor. Significant differences were found between the components of the AERPs and tremor severity and disease duration. This finding implies that ERPs may be useful in evaluating the cognitive functions in ET and that those AERP abnormalities may appear before clinical presentation.