Youth have been the focus of electronic vapor product (EVP) prevention efforts though young adults had similar increases in current EVP use from 2015-2019. This study tested messages to reduce EVP use in young adults. Eight messages on vaping related harms and addictiveness combined with themes on social use and flavors were selected for inclusion in an online randomized controlled trial. Vermont young adults aged 18-24 (n = 569) were randomized to view the eight vaping prevention messages (n = 295) or eight messages on sun safety (n = 274). After completing baseline measures, participants viewed study messages and completed measures on message perceptions and perceived message effectiveness (PME), EVP-related beliefs, and EVP-related harm perceptions. Participants completed EVP-related beliefs and harm perception measures again at 1-month follow-up, as well as measures on tobacco and EVP-related behavioral intentions and behavior (ever and past 30-day use). Intervention participants reported positive impacts on vaping-related message responses. However, findings suggested no effect of vaping prevention messages on EVP-related beliefs, harm perceptions, or behaviors in the full sample. Exploratory analyses in the intervention condition showed that greater PME was associated with lower odds to intent to try cigarettes in the next year at follow-up.