It has been suggested that with age comes experience in how to deal effectively with stressors, and therefore resources needed to uphold constructive leadership behaviors partly depend on managers’ age. This relation between age and leadership behaviors may also depend on the level of support that managers are given. In the present study, we depart from conservation of resource theory and lifespan theory to examine the link between managers’ age and inefficient leadership, with stress as a mediator in this relation. We also investigate whether social support buffers the relations between managers’ age, stress, and inefficient leadership. Self-report survey data from a randomly selected sample of swedish managers were collected at two time points, six months apart. In total, 781 managers answered the survey at both times. We found that, as expected, managers age was negatively related to inefficient leadership through stress. In other words, younger managers perceive themselves as more stressed andnbecause of that more inefficient. Contrary to what we expected, these relations were not influenced by social support. Our study is among the first to study managers’ age as an antecedent to inefficient leadership behaviors. The study also adds to the understanding of this relation by including stress as a mechanism. Furthermore, our research contributes to the examination of potential boundary conditions for when age may translate into stress and inefficient work behaviors by investigating social support as a potential moderator.