Many teachers seek continuous teacher training to increase their pedagogical skills in social and emotional learning (SEL). But how are such benefits sustained in the long-term? This original empirical study is aimed at investigating the stability and change of teachers’ perceived competence, importance and knowledge in SEL before, immediately after and in six months following a Lions Quest (LQ) teachers’ SEL workshop. Participants of this study consisted of 151 teachers and other members of the school staff who participated in the Lions Quest teachers’ two-day workshop. Multivariate analysis of variance (MANOVA) was used to investigate the development of measured competences across time. Results indicated that the perceived competence of the teachers who participated in the LQ workshop increased during the training and stayed at that level for the third measurement six months later, showing a sustainable effect. In addition, knowledge application appeared to improve immediately after the training, but after six months, the effect of the training declined. The importance of the support for promoting teachers’ SEL process is discussed.