Rates of e-cigarette use are high among youth, and there is little known about the long-term health effects of e-cigarettes. Since peer influence is a powerful determinant of tobacco use, we aimed to identify message themes about e-cigarettes that youth would use to encourage or discourage peers from using e-cigarettes. We conducted 10 focus groups (N = 69) with non-smokers and smokers from one middle school, high school and college in Connecticut. Participants engaged in a discussion about e-cigarettes, and each participant created one written message to encourage e-cigarette use and one to discourage use among peers. We content-analyzed the messages and identified three main themes and 12 encouraging and discouraging sub-themes. Encouraging themes included health benefits of e-cigarettes relative to cigarettes, attractive product characteristics (e.g. flavors) and social advantages (e.g. positive social image) of using e-cigarettes. Discouraging messages included health risks of e-cigarettes relative to cigarettes, unattractive product characteristics (e.g. cost) and social disadvantages (e.g. negative social image of using an e-cigarette). Overall, there were no differences by sex, age group or smoking status in generation of encouraging and discouraging message themes. This study identified youth-generated themes that may aid in e-cigarette prevention among youth.