The current study aims to understand the detrimental effects of COVID-19 pandemic on employee job insecurity and its downstream outcomes, as well as how organizations could help alleviate such harmful effects . Drawing on event system theory and literature on job insecurity, we conceptualize COVID-19 as an event relevant to employees' work, and propose that event strength (i.e., novelty, disruption, and criticality) of COVID-19 influences employee job insecurity, which in turn affects employee work and non-work outcomes . We also identified important organization adaptive practices responding to COVID-19 based on a preliminary interview study, and examined its role in mitigating the undesired effects of COVID-19 event strength . Results from a two-wave lagged survey study indicated that employees' perceived COVID-19 event novelty and disruption (but not criticality) were positively related to their job insecurity, which in turn was positively related to their emotional exhaustion, organizational deviance, and saving behavior . Moreover, organization adaptive practices mitigated the effects of COVID-19 event novelty and criticality (but not disruption) on job insecurity . Theoretical and practical implications are discussed . (PsycInfo Database Record (c) 2021 APA, all rights reserved).