Introduction: The goal of this study was to assess the effectiveness of a socio-emotional learning program, RULER, on enhancing both the emotional intelligence and work-related outcomes in Spanish teachers. Measures included: Ability emotional intelligence, assessed by the Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT) and work-related outcomes, such as engagement and burnout. Method: Two private schools from the Autonomous Community of Madrid participated in the study. Once the schools were assigned to experimental or control condition randomly, a total of fifty-four teachers served in the present research, n = 32 teachers participated in the SEL program, n = 22 teachers remained as control group. Results: Multivariate analysis of covariance (MANCOVA) revealed that the SEL group obtained significantly better results in the areas of emotional perception, understanding, and regulation, as also in those related to satisfaction, and commitment to their work, after twenty-four hours of SEL training, across three months, compared with control group. Discussion and Conclusion: These findings expand the literature on the impact of scientific-based programs in the development of personal resources and social and emotional competence in adult population. The paper also discusses practical implications and future research of socio-emotional interventions among adult population, for the development of personal and professional skills, as key factors for an optimal teaching practice.