Although the social-emotional learning model (SEL) has been researched in Vietnam for many years, studies on teachers' SEL-based teaching competence have not been the focus. This study explored the possibility of applying the SEL model to the teaching of Vietnamese primary school teachers. Our case study of 50 teachers who participated in previous SEL projects highlights three factors that prevented successful SEL application in Vietnamese schools, including (a) confusion about the SEL-based teaching perspective, (b) traditional teaching methods, (c) limited training in social-emotional skills, and mental health policies for primary school teachers. The findings have broadened and deepened our understanding of the possibility of successful application of the SEL model in the classroom, which would depend on SEL-based professional supervision, consistency in SEL-based teaching methods and SEL practice guides/manuals, and promotion or adaptation of policies for SEL-based practice and application in schools.