Highly demanding work context of the 21st century reflects itself in workers' high levels of stress, which is particularly evident in the teaching profession. Long-term exposure to teaching duties can result in the occurrence of burnout syndrome, which is best defined by its dimension of emotional exhaustion. To prevent or at least reduce the occurrence of emotional exhaustion, teachers need various resources. The aim of this study was to investigate the role of personality traits and the experience of flow, as personal resources, in reducing emotional exhaustion among teachers, by using longitudinal design. The study involved 808 teachers from 73 secondary schools in Croatia, who were assessed on measures of sociodemographic characteristics, personality (BFI-2), flow (WOLF), and emotional exhaustion at three different points of measurement, respectively. Hierarchical regression analysis showed that gender and age were not significant predictors of emotional exhaustion in the first step. In the second step, when personality traits were added, 22.88% of the variance was explained (with only extraversion and negative emotionality having a significant independent contribution), and in the third step, flow explained an additional 3.81% of the variance in emotional exhaustion beyond the previously introduced variables. Mediation analysis showed that flow is the mechanism underlying the relationship between extraversion and emotional exhaustion, as well as between negative emotionality and emotional exhaustion. Proposed interventions aim to strengthen teachers' resources to help them to cope with stressors in teaching in an effective way.