Empirical data to show whether exposure to e-cigarette advertising stimuli may influence former- and never-smokers to consider vaping is lacking. We examined whether former- and never-smokers’ cognitive, affective, and normative responses to e-cigarette stimuli in retail outlets will predict their vaping intention. A repeat cross-sectional study recruited 876 participants aged 18–24 years at Waves 1 and 2 in the United Kingdom. Bayesian structural equation modeling tested mediation and moderation effects of the variables of interest. Results from Waves 1 and 2 revealed that the association of salience of e-cigarette advertising in stores and gas stations with vaping intention was mediated by affect and subjective norms among former smokers. Cognitive attitudes of never smokers mediated the relationship between salience of e-cigarette advertising in retail outlets and vaping intention at Waves 1 and 2. Former smokers were more likely to hold stronger affect toward vaping than never smokers at Wave 2. Our study supports the need for stronger policies to restrict e-cigarette portrayals in retail outlets, as advertising messages can trigger strong thoughts, feelings, and norms of vaping. Interventions may benefit from including attitudinal and normative components to promote pro-social behavior.