This article presents the impact on cyberbullying of the Asegúrate program. This educational program is based on the theory of normative social behavior, self-regulation skills, and the beliefs held by adolescents and consists in a whole package of strategies and resources to help teachers to include in the ordinary curricula. The evaluation of Asegúrate was carried out with a sample of 4779 students (48.9% girls) in 5th and 6th grade in primary education and compulsory secondary education (M = 12.76; SD = 1.67) through a quasi-experimental methodology, with two measures over time. The instrument used was the European Cyberbullying Intervention Project Questionnaire. The results show that the involvement in cyberbullying as cyber-victim, cyber-aggressor, and cyber-bully-victim increase without intervention, whereas it diminishes when intervention is carried out by the teachers who have received specific training and have used the didactic Asegúrate package. Additionally, the impact of the intervention on the different types of behaviors was analyzed, and the results show that Asegúrate is more effective with some forms than with others. Consequently, the Asegúrate program is effective for decreasing the prevalence of cyberbullying, but some modifications need to be made to impact on all the different forms it can take.