Work ability is a central concept in studies concerning the health of the aging workforce. The aim of the present study was to understand the role of work ability in the Job Demands–Resources model and, specifically, to establish whether and through which mechanisms it operates as a personal resource in the health-impairment process. Two-hundred and 2 female kindergarten teachers aged 50 and over completed self-reporting questionnaires. Data analyses were performed using structural equation model (SEM) and moderated regression analyses. The findings indicated that work ability plays a mediating role in the relationship between job characteristics (that are job demands and job resources) and exhaustion. Conversely, the results showed that work ability did not moderate the relationship between job demands and exhaustion. Overall, the results suggest that work ability can be appropriately considered a crucial resource, which can affect workers’ health and well-being by supporting workers to deal with job demands and optimally use job resources. From a practical point of view, the findings suggest that organizations should implement monitoring actions and intervention programs aimed at fine-tuning job demands and job resources over the entire work life. This can promote the conservation of work ability and, thus, sustain workers’ well-being into the latter stages of their careers.