Background: The acquisition of social and emotional skills is associated with positive youth development, character education, healthy lifestyle behaviours, reduction in depression and anxiety, conduct disorders, violence, bullying, conflict, and anger. School-based interventions aimed to enhance these skills go beyond a problem-focused approach to embrace a more positive view of health; they could also improve the youth's wellbeing. Aim: To describe the main features and to establish the effectiveness of universal school-based RCTs for children and the youth, aimed to promote their psychosocial wellbeing, positive development, healthy lifestyle behaviours and/or academic performance by improving their emotional and social skills. Methods: Systematic review by searching for relevant papers in PubMed/Medline with the following key words: "mental health" OR "wellbeing" OR "health promotion" OR "emotional learning" OR "social learning" OR "emotional and social learning" OR "positive youth development" OR "life skills" OR "life skills training" AND "school". Interval was set from January 2000 to April 2014. Results: 1,984 papers were identified through the search. Out of them 22 RCTs were included. While most interventions were characterized by a whole-school approach and SAFE practices, few studies only used standardized measures to assess outcomes, or had collected follow-up data after ≥ 6 months. The results of all these trials were examined and discussed. Conclusion: Universal school-based RCTs to enhance emotional and social skills showed controversial findings, due to some methodological issues mainly. Nevertheless they show promising outcomes that are relatively far-reaching for children and youth wellbeing and therefore are important in the real world.