This study investigates the joint effects of activities of daily living (ADL) limitation and cognitive impairment on the risk of depression among Chinese older adults aged 65 and above. Using data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS), the researchers found that 27.4% of participants reported depressive symptoms. After controlling for potential confounding factors, both ADL limitation and cognitive impairment were positively associated with depression. The adjusted additive interaction of basic and instrumental activities of daily living limitation was significant, with a combined effect greater than the sum of individual effects. Specifically, the adjusted additive interaction of basic ADL limitation and cognitive impairment was 2.47 (95%CI: 1.92–3.19), and for instrumental ADL limitation and cognitive impairment, it was 3.67 (95%CI: 2.88–4.66). These findings suggest that improving ADL, particularly instrumental ADL, may help reduce the risk of depression among older adults with cognitive impairment. The study highlights the importance of addressing both ADL and cognitive issues to improve the mental health of older adults.This study investigates the joint effects of activities of daily living (ADL) limitation and cognitive impairment on the risk of depression among Chinese older adults aged 65 and above. Using data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS), the researchers found that 27.4% of participants reported depressive symptoms. After controlling for potential confounding factors, both ADL limitation and cognitive impairment were positively associated with depression. The adjusted additive interaction of basic and instrumental activities of daily living limitation was significant, with a combined effect greater than the sum of individual effects. Specifically, the adjusted additive interaction of basic ADL limitation and cognitive impairment was 2.47 (95%CI: 1.92–3.19), and for instrumental ADL limitation and cognitive impairment, it was 3.67 (95%CI: 2.88–4.66). These findings suggest that improving ADL, particularly instrumental ADL, may help reduce the risk of depression among older adults with cognitive impairment. The study highlights the importance of addressing both ADL and cognitive issues to improve the mental health of older adults.