Background: Substance use prevention programs are designed to reduce the influence of risk factors and increase the influence of protective factors. Parents may also affect substance use through conversations that they have with their children. Method: This report uses 2002 to 2015 National Survey on Drug Use and Health (NSDUH) data to assess trends in adolescents’ exposure to substance use prevention messages. It also uses 2015 NSDUH data to examine exposure to prevention messages by age and gender. The 2015 estimates are based on a total sample size of approximately 17,000 adolescents aged 12 to 17. Results: The percentages of adolescents who were exposed to drug or alcohol use prevention messages in the past year through media and school sources and by talking with their parents were generally lower in 2015 than in prior years. In 2015, females were more likely than males to have been exposed to prevention messages through media sources, through school sources, and to have talked with a parent about the dangers of substance use in the past year. Compared to older adolescents, this study found that younger adolescents were more likely to have been exposed to prevention messages in school but less likely to be exposed via the media. Conclusion: Although the majority of adolescents were exposed to substance use prevention messages through the sources assessed in this study, the percentage of adolescents who were exposed to drug or alcohol use prevention messages in the past year through media and school sources declined since 2002. Practitioners, policymakers, educators, and parents should consider the percentage of adolescents who were not exposed to prevention messages through any of these sources.