Background: Although the rates of occurrence of age-related diseases, including presbycusis and cognitive disorders, have increased with an increase in the geriatric population, the relationship between these two conditions remains unclear. Objective: To investigate the association between presbycusis and cognitive disorder. Subjects and Methods: A retrospective review of patient medical records was conducted at a single tertiary university hospital. This study enrolled 399 patients aged ≥65 years who were prescribed hearing aids for the chief complaint of hearing loss. For main outcomes and measures we used audiograms, the Korean Mini-Mental State Examination, and the Global Deterioration Scale (GDS). Results: Of the 399 patients who were prescribed hearing aids for presbycusis, 45 (11.3%) had dementia and 354 (88.7%) did not have dementia. When the cognitive disorder group was divided into mild (1–4) and severe (5–7) subgroups based on the GDS scores, the threshold of hearing loss was significantly higher in the severe group than in the mild group (p < 0.05). The prevalence of dementia was significantly higher in patients with hearing loss for ≥10 years than in patients with hearing loss for <10 years (p < 0.05). Conclusion: Presbycusis and cognitive disorder are correlated. More severe and prolonged hearing loss is associated with a higher prevalence of cognitive disorder.