OBJECTIVE: To evaluate hearing in elderly patients with cognitive impairment by using behavioral and electrophysiological tests before and after the adaptation of hearing aids. MATERIALS AND METHODS: We evaluated 60 elderly patients with sensorineural hearing loss, stratified in groups according to grading by the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog). Subsequently, the patients underwent an initial evaluation before the adaptation of the hearing aid, including the Perceptual Speech Recognition Index (PSR), Gap Detection in Noise (GIN), Long Latency Auditory Evoked Potentials - P300, the Hearing Handicap Inventory for the Elderly (HHIE), self-assessment questionnaires, and the Sentence Recognition Threshold in Noise (S/N). After 3 months of effective use of sound amplification, participants underwent reassessment. The results were subjected to statistical analyses including an analysis of variance (ANOVA) with a significance level of p ≤ 0.05. RESULTS: There were significant differences between the behavioral tests of the 2 groups. The elderly with cognitive impairment had lower performance during both assessment stages. At reassessment after the effective use of hearing aids, there was a significant improvement in performance on behavioral tests, a reduction in P300 latency, and lower perceived participation restriction in both groups. CONCLUSION: Elderly patients with abnormal cognitive function performed worse with regard to skills of speech recognition, auditory closure, and temporal resolution. Acoustic stimulation with hearing aids improves the skills of speech recognition, temporal resolution, and P300 latency, regardless of the cognitive status of the elderly patient.