The sudden onset of the COVID-19 pandemic had a significant impact on all aspects of people’s lives, including their attitudes toward society and psychological well-being. This study aimed to analyze the variation in public trust, perceived societal fairness, and well-being before and after the outbreak of the coronavirus disease 2019 (COVID-19). This study used two-wave longitudinal data of 15,487 residents (2018, T1; 2020, T2) derived from the Chinese Family Panel Studies (CFPS). A repeated measures analysis of variance showed that (a) public trust, perceived societal fairness, and subjective well-being significantly improved and (b) depression significantly increased. Linear regression analysis showed that education and socioeconomic status had a significant predictive effect on public trust, perceived societal fairness, and depression; socioeconomic status had a significant predictive effect on subjective well-being. This study provides evidence and direction for current social governance, namely, policy implementation and pandemic response.