Background <p>Oral functional decline may contribute to frailty in older adults by affecting nutrition, physical performance, and psychosocial well-being. However, longitudinal evidence using rigorous analytic approaches, including competing risk analysis, remains limited. This study examined the association between self-reported oral functional limitation and frailty onset over 4&#xa0;years, with attention to sex differences.</p> Methods <p>We used 4-year prospective data from the Korean Frailty and Aging Cohort Study, comprising 1558 community-dwelling older adults aged 70–84&#xa0;years at baseline (2016). After excluding participants with missing data and baseline frailty, 1348 robust individuals were analyzed. Oral function was assessed using two self-reported items on chewing and pronunciation difficulties. Frailty was defined using the validated Korean Frailty Index. Cox proportional hazards and Fine–Gray competing risk models were applied to evaluate the risk of frailty onset, stratified by sex. Interaction analyses were performed for major comorbidities.</p> Results <p>Oral functional limitation was significantly associated with increased frailty risk (Cox-adjusted HR, 1.74; 95% CI, 1.20–2.53; Fine–Gray-adjusted SHR, 1.70; 95% CI, 1.17–2.46). This association was significant among women (HR, 2.44; 95% CI, 1.52–3.92; SHR, 2.36; 95% CI, 1.46–3.80), but not among men (HR, 0.87; 95% CI, 0.44–1.73; SHR, 0.86; 95% CI, 0.44–1.68). No significant interactions were observed with cardiovascular disease or osteoporosis.</p> Conclusion <p>Self-reported oral functional limitation was significantly associated with frailty onset over 4&#xa0;years, particularly among women. Incorporating oral function assessment into geriatric screening and community health programs may facilitate early identification of risk and the implementation of preventive strategies for frailty.</p>