To examine the impact of social media influencer marketing of foods (healthy and unhealthy) on children's food intake.In a between-subjects design, 176 children (9-11 years, mean 10.5 ± 0.7 years) were randomly assigned to view mock Instagram profiles of 2 popular YouTube video bloggers (influencers). Profiles featured images of the influencers with unhealthy snacks (participants: = 58), healthy snacks ( = 59), or nonfood products ( = 59). Subsequently, participants' ad libitum intake of unhealthy snacks, healthy snacks, and overall intake (combined intake of healthy and unhealthy snacks) were measured.Children who viewed influencers with unhealthy snacks had significantly increased overall intake (448.3 kilocalories [kcals]; = .001), and significantly increased intake of unhealthy snacks specifically (388.8 kcals; = .001), compared with children who viewed influencers with nonfood products (357.1 and 292.2 kcals, respectively). Viewing influencers with healthy snacks did not significantly affect intake.Popular social media influencer promotion of food affects children's food intake. Influencer marketing of unhealthy foods increased children's immediate food intake, whereas the equivalent marketing of healthy foods had no effect. Increasing the promotion of healthy foods on social media may not be an effective strategy to encourage healthy dietary behaviors in children. More research is needed to understand the impact of digital food marketing and inform appropriate policy action.