Adolescents (N = 700) participated in the online survey-based randomized experiment focused on understanding youth perceptions of e-cigarette influencer marketing on social media. Specifically, the study assessed how age appearance of social media influencers, fitness-related contextual framing of e-cigarette content, and perceived influencer credibility jointly shape adolescent harm perceptions, appeal, and susceptibility to e-cigarette use. Participants were randomly shown 6 videos, featuring younger- or older-looking influencers promoting e-cigarettes in the following experimental conditions: 1) younger-looking influencers promoting e-cigarettes alongside fitness-oriented activities (condition 1); 2) older-looking influencers promoting e-cigarettes alongside fitness-oriented activities (condition 2); 3) younger-looking influencers promoting e-cigarettes without any fitness-oriented content; and 4) older-looking influencers promoting e-cigarettes without any fitness-oriented content (control). After watching each video, participants rated perceptions of influencer credibility (i.e., honesty, trustworthiness, knowledge) on the scale of 0 (e.g., dishonest) to 100 (honest). Among all participants, harm perceptions and appeal of e-cigarettes was also assessed. Susceptibility to use e-cigarettes was assessed among never users of e-cigarettes.