Emotional disorders are the most prevalent mental health conditions affecting children and adolescents. Thus, it becomes essential to develop and test early intervention strategies that are accessible, attractive, and can effectively improve their emotional functioning. A randomized control trial compared the prevention effects of the REThink therapeutic game to those of a standard face-to-face prevention program, and a waitlist which was transformed at follow-up into care as usual. Out of 142 healthy children and adolescents who completed the intervention stage, 137 (mean age: 12.84, SD: 1.97) completed a follow-up assessment measuring emotional symptoms, depressive mood and emotion regulation. We also tested potential moderators of its long-term effects, such as parental psychological control, parent attachment and childhood trauma. Our results highlighted the fact that the REThink intervention had a durable impact on the children’s mental health and their ability to regulate their emotions. Moreover, we found that trauma, parent psychological control and parent attachment moderated the maintenance of the improvements. Future research needs to further document how to personalize the game and prevention program components to better address the characteristics of the youths at risk for mental health problems. ClinicalTrials.gov NCT03308981, from 13.10.2017.