The COVID-19 pandemic has constituted a global health crisis that has threatened the mental health of individuals worldwide. The present paper sought to systematically review and meta-analyze studies reporting the prevalence during the COVID-19 pandemic of well-being and psychological distress as defined by the dual-continua model, which includes (absence of) psychological distress and (presence of) well-being among the general population and healthcare workers. Systematic searches were conducted in various databases: PubMed, PsycINFO, Scopus, and Web of Science from inception until 6 December 2020. From a total of 158 studies (N = 880,352) included in the meta-analysis, only seven reported the prevalence of well-being. A random-effect model was used to estimate the pooled prevalence among the general population and healthcare workers on depression (25%; 31%), anxiety (27%; 31%), stress (35%; 32%), and well-being (52%; 45%), respectively. Sub-group analyses based on region, income, percentage of women, preparedness of country to respond to COVID-19, and economic vulnerabilities were conducted in order to examine sources of heterogeneity in psychological distress. Results revealed differences among the two groups and indicated that disparities in terms of preparedness to fight the pandemic can distinctly affect mental health in the general population and healthcare workers. Addressing mental health during and after a health crisis should be in the spotlight of the international and national public health agenda. Considering the protective role of well-being to minimize psychological symptoms, mental health policies during the COVID-19 should include strategies to combat the psychological consequences of the pandemic by promoting well-being practices.