In the frameworks of Job Demands-Resources (JD-R) theory and concepts of competence beliefs, we investigated trajectories of and dynamics between demands and competence beliefs relevant to applied work fields. The study had a longitudinal panel design with eight measurement waves (overall study span of 4 years). Participants (38.1% female) were early career scientists from science, technology, engineering, and mathematics fields who either worked at a university (academia group, n = 1,205) or in industry after having previously worked in academia (industry group, n = 436). We conducted bivariate dual change score modeling and found demands to increase in both groups and competence beliefs to increase in the industry group. While demands accelerated change in competence beliefs in the academia group, competence beliefs accelerated change in demands in the industry group. Implications for JD-R theory and concepts of ability-related self-views as well as practice are discussed.