Background: The COVID-19 outbreak caused severe changes in school activities over the past two years. Teachers underwent a re-planning of their teaching approaches, shifting from face-to-face teaching formats to remote ones. These challenges resulted in high levels of burnout. The identification of risk/protective factors contributing to burnout is crucial in order to inform intervention programs. Thus, we hypothesized a mediation role of teachers’ mentalizing ability (processing of emotions, a component of mentalized affectivity) on the relationship between depression, anxiety, and depersonalization (burnout dimension). Two reverse models were computed. Job satisfaction, teachers’ age and gender, school grade, and length of teaching experience served as covariates. Methods: 466 (M(sd) = 46.2 (10.4) years) online questionnaires were completed by Italian teachers of primary (n = 204) and middle (n = 242) schools. Measures of burnout, depression, anxiety, and mentalization were administered. Results: The findings corroborated our hypotheses: in all models, processing emotions served as a mediator on the relationship between depression, anxiety, and depersonalization, and on the reciprocal one. Job satisfaction positively impacted processing emotion, and negatively impacted depression and depersonalization; women teachers reported high levels of the anxious trait. Conclusions: Overall, it can be concluded that the ability to mentalize has a beneficial impact on teachers’ well-being. Policymaking, clinical, and research implications were discussed.