Participation in community affairs and activities is beneficial to the mental health of older adults. The current study attempted to confirm the mediating role of sense of community (SoC) between community participation (CP) and subjective well-being (SWB), and the moderating role of neuroticism between CP and SoC. A total of 465 older adults aged ≥65 years from China participated in both two-wave online surveys. The self-developed Community Participation questionnaire, the SoC scale, and the Neuroticism subscale were used to assess CP, SoC, and neuroticism, respectively. The four indicators of SWB were assessed by the Satisfaction with Life Scale, Positive Affect and Negative Affect Schedule, and the Center for Epidemiological Studies-Depression scale. The results revealed that CP was associated with three indicators of SWB including life satisfaction, positive affect, and depressive symptoms, SoC mediated the above associations, and neuroticism negatively moderated the association between CP and SoC, after controlling for age, sex, education, spouse status, monthly income, and physical health. CP enhances older adults' SWB through increasing their SoC. When compared to those older adults with a higher score of neuroticism, the enhancing effect of CP on SoC is stronger for those with lower scores of neuroticism.