Abstract: Background:Although tooth loss is known to increase the risk of cognitive impairment and dementia, few studies have investigated the association between functional teeth including rehabilitated lost teeth and cognitive function Objective:We investigated the associations of the numbers of functional teeth and functional occlusal units with cognitive impairment and cognitive function in late life. Methods:The current study was conducted as a part of the Korean Longitudinal Study on Cognitive Aging and Dementia (KLOSCAD), a community-based elderly cohort study. We analyzed 411 participants who have agreed with the additional dental exam. Geriatric psychiatrists and neuropsychologists administered the Consortium to Establish a Registry for Alzheimer’s disease Assessment Packet Clinical and Neuropsychological Assessment Battery to all participants, and dentists examined their dental status. Results:Higher number of functional teeth (OR = 0.955, 95% CI = 0.914–0.997, p = 0.037) and higher number of functional occlusal units (OR = 0.900, 95% CI = 0.813–0.996, p = 0.042) were associated with lower odds of cognitive impairment. When we analyzed these relationships separated by the location of teeth, only the numbers of functional teeth (OR = 0.566, 95% CI = 0.373–0.857, p = 0.007) and functional occlusal units (OR = 0.399, 95% CI = 0.213–0.748, p = 0.004) in the premolar area were associated with lower odds of cognitive impairment. Conclusion:Loss of functional teeth and functional occlusal units (especially in the premolar region) were associated with increased cognitive impairment.