Objectives: This study aimed to investigate the longitudinal associations between the Korean Activities of Daily Living (K-ADL) and the Korean Instrumental Activities of Daily Living (K-IADL) on oral health among older adults. Methods: We analyzed data from 5,735 participants aged ≥55 years using the 7th-9th waves (2018–2022) of the Korean Longitudinal Study of Health and Aging. Oral health indicators included the Geriatric Oral Health Assessment Index (GOHAI) score, the number of implants, the number of natural teeth, and masticatory ability. We employed generalized estimating equations, adjusting for demographic and health-related factors. Results: Superior oral health outcomes were associated with younger age, higher levels of education and income, the presence of a spouse, and economic activity. In contrast, the presence of chronic diseases and activity limitations were associated with poorer oral health. The K-IADL score demonstrated stronger and more consistent associations with all oral health indicators than the K-ADL score. Older adults who the K-IADL score showed to be fully dependent had significantly fewer natural teeth and implants, lower GOHAI scores, and reduced masticatory ability (p<0.05). Conclusions: Our findings demonstrate that K-IADL scores had a stronger association with oral health indicators than K-ADL score. Therefore, early identification of older adults with declining K-IADL score and the provision of tailored oral health services are essential for reducing oral health disparities and promoting equity.