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).