Support to improve teacher wellbeing is scarce in almost all contexts, but especially so in low- and middle-income settings in which teachers face both professional and personal challenges (Kirk and Winthrop 2007; Mendenhall, Gomez, and Varni 2018). In this field note, we discuss War Child's development of Coaching-Observing-Reflecting-Engaging (CORE) for Teachers, an intervention that focuses on improving teachers' wellbeing. CORE is grounded in acceptance and commitment therapy and in the social-emotional framework of the Collaborative for Academic, Social, and Emotional Learning. It also draws from current research, including Jennings and Greenberg's (2009) prosocial classroom model. CORE aims to have a positive influence on classroom climate by providing teachers with the skills and knowledge they need to create an enabling, impactful, and safe learning environment for their students. In this field note, we outline the background on the development of the CORE intervention, including a literature review, the development of a theory of change, and field testing conducted in Chocó, Colombia. Having been field tested and adapted, CORE now is ready for further studies to determine feasibility and effectiveness.