Abstract The rates of adolescent substance use in the U.S. indicate the need for evidence-based prevention programs that include a discussion of alcohol, tobacco, electronic vapor products, marijuana, and opioids. Parents can significantly impact their children’s substance use beliefs and behaviors and are vital to prevention. Unfortunately, many parents feel that they have little influence on whether or not their child uses drugs. While high-quality parent-child communication about substances is a protective factor, parents often find it challenging to effectively engage in these conversations with their children. Youth consume a plethora of media messages that promote and glamorize drugs (e.g., advertising, social media, popular music, television shows), and exposure to these media messages predicts youth substance use. Media literacy education (MLE), which includes the critical analyses of media messages, is an effective approach to youth substance use prevention, including family-based youth prevention programming. The first aim of this project is to create Media World Parent (MWP), a self-paced program designed to provide parents of middle school-aged students with knowledge about teen substance use, media mediation skills, and practice in high quality parent-adolescent communication methods delivered through a highly interactive web-based software application. It is hypothesized that this program will enhance parents’ feelings of efficacy for and participation in open, responsive, comprehensive, and accurate parent-child communication about substance use, including critically analysis of media messages that promote substance use. In turn, we hypothesize that these parent-child conversations will positively impact children’s media literacy skills and outcomes related to substance use (e.g., beliefs, intentions, behavior). The proposed program will utilize a media literacy framework (e.g., Message Interpretation Process model) found to be effective in reducing risk behaviors, including substance use. This project is innovative because the program expands upon a successful theoretical prevention framework, uses MLE to address the typically unaddressed influence of media on youth substance use, covers multiple substances including electronic vapor products and opioids, and uses highly interactive web-based functionality with mobile boosters. The program will be iteratively developed and refined with input from a diverse Advisory Panel of parents, youth, and prevention specialists. The second aim is to conduct a feasibility study of the MWP program in which a diverse sample of parent-child pairs (N=286) are randomly assigned to an intervention group (MWP) or an active control group (e.g., medically-accurate web content on adolescent substance use). Parents and youth will complete pre-post assessments, which will provide a preliminary test of program effectiveness for positively affecting outcomes. Program feedback ratings will also be used to ev...