Children are active on social media and consequently are exposed to new and subtle forms of food marketing.To examine whether exposure to a YouTube video featuring influencer marketing of an unhealthy snack affects children's ad libitum snack intake and whether inclusion of an advertising disclosure moderates this effect.In a randomized between-subjects design, 151 children (aged 9-11 y; mean, 10.32 y ± 0.6) were exposed to influencer marketing of a non-food product (n = 51), or an unhealthy snack with (n = 50) or without (n = 50) an advertising disclosure. Participants' ad libitum intake of the marketed snack and an alternative brand of the same snack was measured.Children exposed to food marketing with (P < .001, d = 1.40) and without (P < .001, d = 1.07) a disclosure consumed more (kcals) of the marketed snack relative to the alternative; the control did not differ (.186, d = 0.45). Consumption of the alterative brand did not differ across conditions (.287, η = .02). Children who viewed food marketing with a disclosure (and not those without) consumed 41% more of the marketed snack (.004, η = .06), compared with control.Influencer marketing increases children's immediate intake of the promoted snack relative to an alternative brand. Advertising disclosures may enhance the effect.