The teaching of social and emotional learning (SEL) is internationally regarded as supporting a range of short- and long-term student outcomes, including improved academic performance and increased prosocial behaviour. Teachers are widely acknowledged as critical to delivering SEL in schools and students’ SEL outcomes. Despite SEL’s increasing presence within Australia’s education policy frameworks, school programs and the national curriculum, few studies have investigated Australian primary (K–6) teachers’ professional SEL knowledge or practices. A better understanding of teachers’ interpretations and implementation of SEL is required to inform evolving research, programming, teacher training and policymaking in this area. The study uses a qualitative experiential research approach to address gaps and identified needs in the SEL literature. This involves multiple case study methodology and teacher-centred data collection methods—including interviews, observations and video-stimulated reflective dialogues—to generate detailed insights about how teachers understand, plan and teach SEL. The findings of this study showcase teachers as central to the creation and development of SEL-enhancing learning environments. The findings indicate that teachers facilitate SEL based on what they know and value, in response to their students’ needs, in line with their school programs, and with their colleagues’ support. The findings support and extend existing SEL literature. They highlight the significant influence that teachers’ combined personal knowledge, personal and professional experiences, and school-based relationships have on their teaching of SEL. Insights from this study support emerging directions for the practice and programming of SEL initiatives in schools and further theoretical discussions of the role of teachers’ social and emotional competence (SEC) in existing teacher knowledge and professional training models.