Public health campaigns have the potential to correct vaping misperceptions. However, campaigns highlighting vaping harms to youth may increase misperceptions that vaping is equally/more harmful than smoking. Vaping campaigns have been implemented in the United States and Canada since 2018 and in England since 2017 but with differing focus: youth vaping prevention (United States/Canada) and smoking cessation (England). We therefore examined country differences and trends in noticing vaping campaigns among youth and, using 2022 data only, perceived valence of campaigns and associations with harm perceptions. Seven repeated cross-sectional surveys of 16-19 year-olds in United States, Canada and England (2018-2022, n = 92 339). Over half of youth reported noticing vaping campaigns, and noticing increased from August 2018 to February 2020 (United States: 55.2% to 74.6%, AOR = 1.21, 95% CI = 1.18-1.24; Canada: 52.6% to 64.5%, AOR = 1.13, 1.11-1.16; England: 48.0% to 53.0%, AOR = 1.05, 1.02-1.08) before decreasing (Canada) or plateauing (England/United States) to August 2022. Increases were most pronounced in the United States, then Canada. Noticing was most common on websites/social media, school and television/radio. In 2022 only, most campaigns were perceived to negatively portray vaping and this was associated with accurately perceiving vaping as less harmful than smoking among youth who exclusively vaped (AOR = 1.46, 1.09-1.97). Consistent with implementation of youth vaping prevention campaigns in the United States and Canada, most youth reported noticing vaping campaigns/messages, and most were perceived to negatively portray vaping.