Media-related cognitions are a unique influence on adolescents’ substance use outcomes even after accounting for the powerful influence of parent and peers. This cross-sectional study expands upon prior research by investigating the impact of media-related cognitions on children’s alcohol and tobacco outcomes in the context of parental and peer substance use. Six hundred forty-nine elementary school children (M = 9.4 years of age, SD = 1.1 years; 51 % female) completed self-report questionnaires. After accounting for peer and parental substance use, children’s media-related cognitions were independently associated with three outcomes: preferences for alcohol-branded merchandise, moral beliefs about underage alcohol and tobacco use, and intentions to use alcohol and tobacco. Children’s perceptions of the desirability and realism of alcohol and tobacco ads—and their similarity to and identification with these ads—predicted greater intentions to use. Desirability and identification with alcohol and tobacco ads were associated with stronger preferences for alcohol-branded merchandise, and understanding advertising’s persuasive intent predicted weaker preferences. Media deconstruction skills predicted stronger beliefs that underage alcohol and tobacco use is wrong. Peer and parental substance use were associated with stronger substance-use intentions among children and weaker feelings that substance use is wrong. The findings highlight the role of media influence in contributing to youth substance use and the potential role of media literacy education in the early prevention of substance use.