Drawing on the transactional theory of stress and the person–situation interactionist perspective, we theorize that the indirect effect of challenge stressors on affective commitment through work engagement is moderated by the joint effects of core self-evaluations and perceived organizational support. In a sample of 226 Chinese public servants, we tested a new moderated moderated (three-way) mediation model using structural equation modeling. Our results show that challenge stressors positively influence work engagement, which has a significant positive effect on affective commitment. Moreover, the indirect effect of challenge stressors is maximized when both perceived organizational support and core self-evaluations are high.