The idea of introducing social and emotional learning in educational settings is based on the assumption that emotions are an essential element of school life. Emotional competencies are conducive to student learning and well-being, in addition to conveying emotional resources for teachers and educators. The development of such abilities is a prerequisite for students and teachers to engage in productive and enjoyable classroom dynamics. Indeed, well-developed emotional competence enhances students’ psychological adjustment, self-esteem, adaptive coping with stress at school and academic success. However, engaging in disruptive behaviors and school violence (bullying) may be attributed to a deficit in students’ social and emotional development. Similarly, being emotional intelligent is also a crucial skill for teachers, as educational work includes expressing empathy and support and displaying appropriate emotions during teaching, which enhances students’ learning. Research has stressed the protective role of teachers’ emotional competencies regarding mental health problems, such as depression, anxiety and work-related stress (burnout). The objective of the present research was to examine the impact of emotional competence on psychological adjustment, subjective well-being and mental health, in both student and teacher populations in a school context. Given the characteristics of a multi-paper thesis, six studies have been included that provide the scaffolding for this research. The studies 1-4 focused on the development of emotional competence in relation to psychological adjustment and subjective well-being in adolescent students. The studies 5-6 addressed the study of emotional intelligence in teachers in relation to mental health issues, specifically burnout. In view of the results obtained by the six studies, the ESCQ-21 has been found to be a reliable and valid tool for measuring emotional competence in Spanish adolescents. Furthermore, students as well as teachers benefit from well-developed emotional competencies. While emotional competence in adolescents was associated with social-emotional adjustment and subjective well-being, in teachers emotional intelligence predicted mental health outcomes. A couple of mediators, such as self-esteem, perceived stress and affectivity have been suggested that might explain the psychological mechanisms that underlie the link between emotional development, mental health and well-being. Finally, socio-emotional intervention programs have been shown their effectiveness for a wide range of positive outcomes in students and teachers. For instance, they may be considered valuable tools for preventing bullying among peers and alleviating teacher burnout. Drawing from these findings, the dissertation makes a relevant contribution to the existing literature that stresses the benefits of developing emotional competence for psychological adjustment, mental health and well-being among students and teachers.