The present paper focuses on social and emotional learning, and highlights empirical findings on its importance for teachers, students and schools. The importance of social and emotional learning in school settings has been a central focus of research for the last 30 years. The development of teachers’ social and emotional competencies has been an essential factor for improving social and emotional learning of students. Only when teachers are able to create a school climate in which students feel included and welcome, students can develop and enhance their social and emotional competencies. In this paper, we outline the main conceptual frameworks on social and emotional learning, emphasizing the CASEL framework, relevant for both young people and adults. We proceed by focusing on teachers’ social and emotional competencies, as teachers are one of the key figures for fostering and developing social and emotional competencies in school settings. Afterwards, we address the issue of development of teachers’ social and emotional competencies in various settings. The last part of the paper links teachers’ and students’ social and emotional competencies. We stress the importance of teachers’ social and emotional competencies for healthy teacher-student relationships, and students’ well-being and academic achievement. As teachers also need support for the development of these competencies, we advocate for comprehensive school-wide approach, in order to ensure the successful implementation of social and emotional learning in classrooms.