Background: The demand for certified nurse aides (CNAs) in long-term care institutions is gradually increasing. Factors such as well-being that positively influence the work of CNAs have been inadequately explored in the literature. Purpose: This study was designed to examine the relationships among social support, self-efficacy, demographics, and psychological well-being in CNAs during the recent COVID-19 pandemic and to assess the moderating role of social support on self-efficacy and well-being in this population. Methods: In this quantitative correlational study, CNAs from 24 legally registered long-term care institutions were recruited as participants. Data were collected using a demographic questionnaire, the General Self-Efficacy Scale, the Social Support Scale, and the Chinese Happiness Inventory. Partial least squares structural equation modeling was used to test the research hypotheses model. The Strengthening the Reporting of Observational Studies in Epidemiology checklist was followed in this cross-sectional study. Results: A total of 148 CNAs were enrolled as participants. The mean age of the participants was 46.48 years. Social support and having children were identified as being significantly and positively correlated with well-being, and self-efficacy was identified as having no significant impact on well-being. Importantly, social support was found to moderate the relationship between self-efficacy and well-being. Overall, social support and having children were important predictors of well-being, with a combined explanatory power of 41.6% (Q^2 = .28, f^2 = 0.40). Conclusions/Implications for Practice: Self-efficacy was found to be less predictive of well-being in the presence of higher levels of social support. Being a parent was also identified as an important factor affecting the well-being of CNAs under stress. Managers of long-term care institutions should intervene to improve the CNA's social support. Also, CNAs who do not have children should pay more attention to their well-being.