To date, effective body image interventions for preadolescent school girls are lacking. The present study sought to evaluate the effectiveness of Y's Girl, a published body image curriculum specifically tailored for preadolescent school girls. A sample of 60 Grade 6 girls with a mean age of 11.25 (range of 11-12) years were allocated either to an intervention or control group and completed baseline and posttest measures of body image, thin-ideal internalization, body comparison, self-esteem, peer factors, and disordered eating. Findings revealed that, compared to the control group, girls receiving the intervention reported improved body image, thin-ideal internalization, body comparisons, and self-esteem at posttest 1 week after the intervention ended. Furthermore, changes in body satisfaction were moderated by initial levels of risk-factors. These findings provide initial support for Y's Girl as an effective, affordable body image intervention for preadolescent girls which can be implemented by teachers.