In this diary study, we investigated multi-level predictors of daily counterproductive work behavior (CWB) relying on the theoretical frameworks of affective events theory and the emotion-centered model of CWB. We assessed significant work events, event-based fairness perceptions, negative emotional reactions to work events, and employee CWB over a 10-day period. We tested within-person relations predicting CWB, and cross-level moderating effects of two emotion regulation strategies (suppression and reappraisal). Results from a multi-level path analysis revealed that significant work events had both direct and indirect effects on negative emotional reactions. Further, negative emotional reactions in turn mediated the relationships between significant work events and all forms of daily CWB as well as the relationship between event-based fairness perceptions and daily CWB-O. Results also supported the moderating role of reappraisal emotion regulation strategy on relations between significant work events and negative emotional reactions. Less support, however, was found for the moderating influence of suppression on the link between negative emotional reactions and CWB. Among the broad work event categories we identified, our supplemental analyses revealed that negative work events involving interactions with supervisors elicited the highest levels of employee negative emotional reactions. We discuss the theoretical and practical implications of these findings. Copyright © 2014 John Wiley & Sons, Ltd.