Background <p>China has entered an aging society, and the mental health of the aged has gradually attracted social attention. This study aimed to model the mediating effect of social activities on the relationship between incapacitation and depression in the aged and to explore the moderating effect of community support on the mediating role.</p> Methods <p>This paper used the latest data from The Chinese Longitudinal Healthy Longevity Survey (CLHLS). A moderated mediation effect model was constructed with the degree of incapacity as the independent variable, depressive symptoms as the dependent variable, socialization as the mediator, and community support as the moderator.</p> Results <p>Socialization was a partial mediating variable in the relationship between incapacitation and depression in the aged, and its mediating effect accounted for 13.29% of the total effect. The moderating effect of community support on the mediating role of socialization was significant (B = -0.006, SE = 0.003, 95% <i>CI</i>: -0.014 ~ -0.001), but it moderated only the second half of the model, which is the relationship between social activities and depression.</p> Conclusions <p>(1) There was a significant positive correlation between disability and depression in the aged. (2) Socialization partially mediated the relationship between disability and depression in the aged. (3) Community support moderated only the relationship between social activities and depressive symptoms, whereas it did not affect the relationship between disability and social activities.</p>