As children’s usage of the Internet increases, so does the frequency of child-targeted advergames on the Internet. Despite the potential negative effects of advergames on children's diet and health, few studies have systematically examined how children in South Korea understand advergames and the extent to which these games affect children. This study examined second and third graders' understanding of online advergames, their impact on food choices, and the effect of an educational program on advergames. Children in the experimental group were exposed to the educational program on advergames, while those in the control group played a science education game on planets. As a distractor, children played a hidden catch game before all participants played an ice-cream advergame. Results showed that very few children recognized the commercial intentions of the advergame. Both the recognition of an advertiser’s existence and the detection of the persuasive intent were minimal, and the educational program on advergames did not make any significant differences. However, those who recognized the persuasive intent were less likely to select the advertised food category, as the detachment effect predicts. Persuasion Knowledge Model was used as a theoretical frame, shaping a discussion on the importance of children's recognition of persuasive intent and appropriate policy recommendations.