Within the Job Demands-Resources model, the presence of job demands (e.g., work pressure) and the absence of job resources (e.g., social support) relate to burnout through a psychological energetic process, whereas the presence of job resources associates with work engagement through a motivational process. Although various mechanisms have been suggested to understand these processes, empirical evidence for these mechanisms is scarce within the JD-R framework. This study examines the role of basic need satisfaction, as defined within Self-Determination Theory, in the relationships between job demands, job resources, and employees' exhaustion and vigour, the main components of burnout and engagement, respectively. Structural equation modelling in a heterogeneous sample of 745 employees of the Dutch-speaking part of Belgium confirmed that satisfaction of basic psychological needs partially explained the relationships from job demands to exhaustion and from job resources to vigour. It fully accounted for the relationship between job resources and exhaustion. We conclude that the current study adds to the research pointing at need satisfaction as a promising underlying mechanism for employees' thriving at work.