Adolescents and young adults continue to use e-cigarettes, and communication campaigns are needed to decrease use among these populations. We developed and tested a point-of-sale communication campaign focused on e-cigarette chemical exposure. We developed messages based on formative research and tested them (versus text-only messages) in a nationally-representative online survey among adolescents and young adults (16-25) (Phase 1). Based on survey findings, we selected a message focused on nicotine and brain development for the point-of-sale trial (Phase 2). We then conducted a cluster-randomized trial at six gas stations with convenience stores, randomly assigned to the intervention (messages displayed) or no message control condition. We conducted intercept surveys with repeated cross-sectional samples of 50 participants (ages 16-25) per store, at baseline and a four-week follow-up. Phase 1 included 1,636 participants in the online study. Intervention messages were rated as more attention grabbing than plain text messages (p < .05), though were rated similarly on other outcomes. Exposure to intervention messages resulted in larger changes from pre- to posttest for beliefs about addiction and relative harms versus cigarettes (p < .05). Phase 2 included 586 participants in the point-of-sale study. Real-world campaign exposure was low (31.8%), and no differences were found between conditions. E-cigarette prevention messages focused on nicotine's impact on brain development show promise. However, garnering attention for communication campaigns in saturated point-of-sale environments, often dominated by tobacco advertising, is challenging. Future efforts should utilize additional communication channels to directly target adolescents and young adults.