The social distancing, confinement and quarantine adopted since March 2020 to confront the COVID-19 pandemic have affected multiple vital areas, and specially work, business and productive activities. Prior research has highlighted the relation between perceptions of risk in employment and its concomitant financial risk with a myriad of consequences for people's well-being and health. In order to analyze the potential negative consequences of temporary layoffs, downsizing or closure of companies and businesses, and the consequent insecurity about the continuity of employment, the aim of this study is twofold. Firstly, to analyze the relations between the perceptions of job insecurity and financial threat and overall mental health during the first month of the COVID-19 pandemic in a sample of the Chilean adult population. And secondly, to identify the potential buffer effect of perceived social support on this relation. To analyze this, we carried out a cross-sectional study on a non-probabilistic sample aimed at a general Chilean adult population. The results show that both perceptions of job insecurity and financial threat are associated with a decline in perceived mental health. Additionally, results indicate a moderate buffer effect of perceived social support relative to the size of the social network. Thus, in relation to job insecurity and financial threat, the network size mitigates the association of both with the decline in perceived mental health. The theoretical and applied scope of these findings are analyzed, and their challenges and limitations are discussed.