This study aimed to explore the association between dependency and cognitive function among older adults. A combined cross-sectional and longitudinal study was conducted in 26 locations in China. A total of 1160 participants aged ≥ 60 years were selected using a complex multistage sampling design, and 152 participants completed data collection after one year follow-up observation. A questionnaire was administered by face-to-face interviews. Dependency was measured using the standardized Chinese version of the Minnesota Multiphasic Personality Inventory-II. Logistic regression analysis was conducted to assess the association between dependency and cognitive function. Cox proportional hazards analysis was performed to identify causality between cognition function and dependency. The results of logistic regression analysis showed that the orientation and outdoor instrumental activities of daily living (IADL) domains were significantly associated with dependency, with odds ratios of 1.45 (95% CI, 1.26–1.67; p < 0.001) and 1.16 (95% CI, 1.06–1.26; p < 0.001), respectively. In the Cox proportional hazards analysis, the DASC-21 score was significantly associated with dependency, with hazard ratio of 1.32 (95% CI, 1.03–1.69). The causality between cognition impairment and dependency was identified, and the orientation and outdoor IADL domains were significantly associated with dependency.