Over the past 3 years, employees have constantly witnessed how their organizations have responded to the challenges posed by the COVID-19 pandemic. Here, we hypothesize that employees' perceptions of the COVID-19 safety climate of their organization positively affect their vaccine readiness. To examine the underlying mechanisms of this effect, we use a self-perception theory lens. Thus, we hypothesize that an organization's COVID-19 safety climate affects employees' COVID-19 vaccine readiness through employees' adherence to COVID-19 guidelines. We conducted a time-lagged study over the time span of 1 year (N = 351) to test our hypotheses. In general, results support our hypotheses. In particular, results showed that perceived COVID-19 safety climate assessed at an early stage of the pandemic (April 2020, when no vaccines were available) predicted employees' COVID-19 vaccine readiness more than a year later. In line with self-perception theory, this effect was mediated by employees' adherence to COVID-19 guidelines. The present study provides theoretical insight into the underlying mechanisms of organizational climate on employees' attitudes. From a practical perspective, our results suggest that organizations are a powerful lever for promoting vaccine readiness.