Because of scarce research, the effectiveness of substance abuse prevention in leisure settings remains unclear. In this study, we evaluated the effectiveness of a peer-led educational prevention measure with adolescent groups in unstructured leisure settings, which is a component of the complex German nationwide 'Na Toll!' campaign. Using a cluster-randomized two-group post-test-only design, we tested whether the measure influenced component-specific goals, namely risk and protective factors of alcohol use such as risk perception, group communication and resistance self-efficacy. The sample consisted of 738 adolescents aged 12-20 years who were recruited at recreational locations and completed an online questionnaire 1 week after the peer education or recruitment event. Sixty-three percent of the sample participated in the 3-month follow-up assessment. Data analysis revealed post-test effects on risk perception, perceived norm of alcohol communication in the peer group and resistance self-efficacy. Follow-up effects were not observed, with the exception of a significant effect on risk perception. In conclusion, the peer-led education measure in leisure settings might have supported the adolescents in this study to perceive alcohol-related risks, to feel accepted to talk about alcohol problems with their friends and to be more assertive in resisting alcohol use in the short term.