BACKGROUND: California boasts the largest regulated cannabis market in the world, but it is increasingly exposing youth to cannabis marketing, and the state's definition of content appealing to youth is vague. We aimed to identify the specific features of California cannabis ads that increase interest in cannabis use among adolescents to inform reasonably restrictive marketing policy. METHODS: Participants consisted of 409 youth (age 16-20 years) susceptible to using cannabis in the future and living in California. Using an online experiment, participants were randomly assigned to view cannabis ads with and without features previously shown to be appealing to adolescents, followed by questions about attitudes toward the ad and their interest in using the advertised cannabis product or service. Multivariable regressions tested associations of content features with these outcomes. RESULTS: Several features were significantly associated with increasing youth interest in cannabis use and attitudes toward the ad following ad exposure, including illustration, clear product descriptions, food or flavor references, depictions of positive sensations, adventure, psychoactive effects, and references to heavy consumption. CONCLUSION: California cannabis ads contain features that appeal to youth and that are not restricted in California or other U.S. states with legal cannabis retail.