BackgroundThe high frequency of eating disorders (EDs) in sports speaks of a need for early‐stage preventive measures.ObjectivesThis study evaluated the acceptability of an age, sex, and sports adapted version of the “Body Project” and changes in mental health symptoms.MethodsThis noncontrolled pilot study included a class of athletes from 18 sports (N = 73, 13–14 years) at a sport‐specialized junior high school in six small‐group workshops. We interviewed 34 athletes on program acceptability, and all athletes responded to questionnaires at pretest, posttest, and 6‐month follow‐up including the Body Appreciation Scale 2–Children, Social Attitudes towards Appearance Questionnaire‐4 revised, Eating Disorder Examination Questionnaire Short form‐12 modified, and questions about body appearance pressure (BAP).ResultsAthletes found the program acceptable and beneficial, but some missed physically oriented activities or did not identify with the focus, particularly boys. There were acceptable levels in mental health constructs before the workshops. There were temporary changes in the percentage of boys experiencing “BAP in society” by −14.8% points (95% CI: −.6 to .0, p = .04), % in total group experiencing “BAP at school” by +11% points (95% CI: .0–.2, p = .05), thinness idealization by girls (g = .6, p = .002) and total group (g = .4, p = .006), and muscularity idealization by boys (g = .3, p = .05) and total group (g = .23, p = .04).DiscussionAthletes experienced benefits from the Young Athlete Body Project. Seeing stabilization in outcomes may mean a dampening of the otherwise expected worsening in body appreciation and ED symptoms over time.Public SignificanceAdolescent athletes are at risk for developing EDs. Due to lack of prevention programs for this group, we adapted and evaluated a well‐documented effective program, the Body Project, to fit male and female athletes <15 years. The athletes accepted the program and experienced participation benefits, with stronger acceptance among girls. Our promising findings encourage larger scaled randomized controlled trials to further evaluate a refined version this program among very young athletes.