Using the Conservation of Resources (COR) theory as a framework, we hypothesized a maladaptive role played by overcommitment in the escalation of burnout. We further specified our model by testing an interaction effect of job satisfaction. By using a longitudinal design, we proposed a moderated mediational model in which burnout at Time 1 (T1) increases overcommitment, which in turn leads to more burnout one month later. We further expected to find a moderating role of job satisfaction in the link between overcommitment and burnout at Time 2 (T2). A group of 86 white-collar workers in personnel services in Italy (longitudinal response rate = 77.48%) participated in our study. The findings supported our hypotheses even when controlling for gender and role stressors. In particular, by using bootstrapping procedures to test mediation, we found evidence that employees reporting burnout tend to develop a maladaptive coping style, i.e., overcommitment, which in turn increases burnout over time. This relation was particularly strong for dissatisfied employees. These results highlight the importance of overcommitment for burnout escalation, as well as of job satisfaction, since it may mitigate, at least in the short term, the effect of such dysfunctional strategies.