<p>The issue of disability among older adults is increasingly recognized as a critical concern across domains such as family dynamics, public health, and social security. Disability not only compromises the quality of life of older individuals but also imposes substantial burdens on family caregivers and the broader social welfare system. However, existing studies often focus on the linear “net effects” of individual variables, overlooking the interplay of multiple factors and thereby failing to fully capture the complex mechanisms underlying elder disability. Based on nationally representative data from the 2020 wave of the China Health and Retirement Longitudinal Study (CHARLS), and grounded in the biopsychosocial model of medicine, this study employs fuzzy-set Qualitative Comparative Analysis (fsQCA) to systematically examine how configurations of eight condition variables contribute to the disability process among older adults. These variables encompass moderate-to-vigorous physical activity, low-intensity physical activity, and chronic illness, depression, self-rated health, emotional support, financial support, and daily care. The findings reveal that: (1) Six representative configurational pathways leading to disability are identified, underscoring the non-linear nature of the disability process in older adults; (2) In the absence of financial support and emotional comfort, the provision of daily care often co-occurs with adverse physical and psychological conditions, acting as a risk factor for disability; (3) Lack of both moderate-to-vigorous and low-intensity physical activity significantly increases the risk of disability; (4) Chronic illness is a necessary condition for disability, serving as an indispensable physiological prerequisite. This study contributes to a nuanced understanding of the multifaceted mechanisms behind elder disa and offers empirical evidence for developing more targeted, stratified, and differentiated intervention strategies.</p>