This study aimed to advance understanding of the relation between social media and adolescent alcohol use while accounting for offline peer alcohol use, exploring offline peer alcohol use separately as a covariate and as a moderator, with an additional exploratory analysis of the relation between social media and alcohol use without offline peer alcohol use in the model. A total of 868 students (55% female) in grade 7 (n = 468) and grade 8 (n = 400) at wave 1, self-reported on alcohol use, binge drinking, and social media use as well as nominated friends from their school and grade. Data from nominated peers who also completed the questionnaires were used for peer-report of alcohol use. Data were collected annually from students at grades 8, 9, 10, and 11 were used in analyses. Final structural models consisted of a cross-lagged panel design with saved factor scores for social media and peer alcohol use predicting a categorical alcohol use variable or a binary binge drinking variable. With offline peer alcohol use as a covariate in the model, social media did not prospectively relate to subsequent grade alcohol use or binge drinking. However, without offline peer alcohol use, the path from social media use to subsequent grade alcohol use was significant but not the path to binge drinking. Offline peer alcohol use did not significantly moderate the relation between social media and subsequent grade alcohol use or binge drinking.