Objective: Body image and eating disorder interventions based on cognitive dissonance have been shown to be effective among girls and women aged 14 and above. This article reports a preliminary examination of whether a dissonance intervention is also effective when delivered in a school setting to 12- and 13-year-old girls in the United Kingdom Method: Girls (N =106, mean age =12.07 years, SD =.27) were allocated to the intervention condition or a waitlist control. Results: In contrast to the control group, girls in the intervention condition reported significant reductions in body dissatisfaction and internalization of a thin body ideal post-intervention. There was no significant change in self-reported dietary restraint for either condition. In addition, compared with the control group, girls in the intervention condition showed increased resilience to negative media effects 1-month post-intervention. Conclusions: Results suggests that dissonance based programs can reduce body dissatisfaction, internalization and negative media effects among a younger group of girls than previously examined and in an United Kingdom school setting. © 2013 American Psychological Association.