<p>The aim of the current study was to investigate the effects of a co-created, multi-component and community-based intervention on adolescent perceptions of social norms relating to alcohol, parental rules about alcohol, and the formal (outside home) and informal (inside home) perceived accessibility of alcohol. A quasi-experimental, longitudinal design was employed with one experimental municipality (52.6%) and one control municipality (47.4%). A sample of <i>N</i> = 2165 adolescents (M_age = 14.2, <i>SD</i> = 1.32, 51% girls) filled out two annual online questionnaires. Results demonstrated that adolescents in the intervention municipality displayed significantly lower levels of positive general norms towards alcohol than adolescents in the control municipality (<i>β</i>=-0.09, <i>p</i>&lt;.001). Moreover, adolescents in the intervention municipality indicated perceiving alcohol as less accessible both within their own home (informal; <i>β</i>=-0.10, <i>p</i>&lt;.001) and in formal settings (café, bar, etc.; (<i>β</i>=-0.11, <i>p</i>&lt;.001). Additionally, they reported experiencing stricter rules from their parents about alcohol (<i>β</i> = 0.09, <i>p</i>&lt;.001). This study supports a whole-community approach to alcohol prevention by reducing parental and community factors that influence adolescent alcohol use.</p>