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Exposure to e-cigarette marketing on social media is a risk factor for e-cigarette use among youth. Tobacco brands use influencers to promote e-cigarettes on social media; however, influencer marketing has not been sufficiently studied. This study explored network connections and interactions through comments on social media posts between global nano- and micro-influencers (influencers with approximately 1,000 to 100,000 followers) and their audiences on Instagram and TikTok. We constructed directed unipartite networks among Instagram (N = 104) and TikTok (N = 100) influencers and users on Instagram (N = 55,622) and TikTok (N = 68,673) who commented on these influencers' posts in 2021–2022 (including influencers who commented on each other's posts). Comments to posts of users who were not classified as influencers were not collected. The Instagram network was denser (more interconnected) and more active compared to the TikTok network (1.48 times as high density, 281 times as high transitivity, and 86 times as high reciprocity). Both Instagram and TikTok networks contained heterophilic ties (i.e., influencers from different geographic regions such as Asia, North America and Europe connected to each other), indicating that influencers from different geographic regions engage with (comment on) each other's content, potentially exposing audiences to a wide variety of e-cigarette content. Influencers who promote e-cigarettes and post about lifestyle topics (e.g., fitness, fashion, gaming) occupy more central positions in the Instagram and TikTok networks than influencers who focus primarily on e-cigarette promotion, potentially exposing users who are not interested in tobacco-related content to harmful imagery of e-cigarettes. The findings emphasize the need for strengthening influencer marketing regulation on social media platforms popular among youth. [Display omitted] • The Instagram network is denser than the TitkTok network. • Influencers from different regions engage with each other's content, likely exposing users to diverse e-cigarette content. • Influencers posting about e-cigarettes and lifestyle could expose users uninterested in e-cigarettes to e-cigarette posts. • The study's findings highlight the need for stronger influencer marketing regulations on social media popular among youth. [ABSTRACT FROM AUTHOR]