Accumulating evidence indicates that social media use (SMU) enhances life satisfaction among older adults, yet further research remains necessary to elucidate its underlying mechanisms. This study investigated whether SMU affects older adults’ life satisfaction through online and offline social connectedness and whether loneliness and functional disability moderate these pathways. 232 Chinese older adults ( M = 65.28, SD = 6.77) completed questionnaires assessing SMU, online and offline social connectedness, loneliness, functional disability, and life satisfaction. Results showed: (1) online and offline social connectedness played mediating roles between SMU and life satisfaction; (2) loneliness moderated the association between SMU and online social connectedness, with the mediation effect significant only for older adults experiencing higher loneliness; and (3) functional disability moderated the link between SMU and offline social connectedness, with the mediation effect significant only for those with greater functional disability. These findings could inform targeted interventions to advance successful aging.