Introduction: In recent years many schools have introduced peer mediation as a method to improve coexistence. However, little has been done in the way of empirical evaluation of school mediation services. The aim of this research, therefore, was to understand the benefits of mediation from an educational and transformational perspective, by analyzing how it has promoted socio-emotional learning in student mediators. Method: The perception of social-emotional learning acquired through mediation was analyzed in a sample of 157 student mediators, including both active and former mediators from 10 public and private/charter schools in Malaga. We also analyzed how certain variables of the mediation process and the social validity of that process relate to the perception of socio-emotional learning. In addition, the perspective of the former mediators was analyzed in order to learn whether their learning outcomes are maintained and transferred to other areas of life. Results: Students perceived that their experience as mediators has fostered the acquisition of socio-emotional learning, emphasizing empathy, neutrality, alternative thinking and the importance of knowing how to ask for help. In addition, the number of mediations in which they had participated, and the perception of utility and social validity were positively related to the development of socio-emotional learning. It should be noted that no significant differences were found between the learning outcomes reported by the active mediators and by the former mediators, although the latter were better able to identify the specific benefits gained from the school mediation experience. Discussion and conclusions: Peer mediation, besides being a method for managing conflicts and for improved coexistence at school, promotes socio-emotional learning in peer mediators; this learning is maintained over time and extends beyond the school context. Study findings support the educational and transformational potential of school mediation.