The Job Demands–Resources (JD-R) model postulates that job demands and job resources constitute two processes: the health impairment process, leading to negative outcomes, and the motivational process, leading to positive outcomes. In the current research we extended the JD-R model by including both counterproductive work behaviour (CWB) as a behavioural stress-reaction and job-related affect as a mediator in both processes. In a sample of 818 public-sector employees we found support for a model where job demands (workload, role conflict, and interpersonal demands) were associated with abuse/hostility CWB, whereas job resources (decision authority, social support, and promotion prospects) were associated with work engagement. Furthermore, job-related negative affect mediated the relationship between job demands and abuse/hostility CWB, whereas job-related positive affect mediated the relationship between job resources and work engagement. We also found that the impact of job demands on negative affect was attenuated by job resources.