OBJECTIVE : To evaluate the immediate post-intervention and 6-month post-intervention effects of a Brazilian school-based randomized controlled trial for girls targeting shared risk factors for obesity and disordered eating. METHODS : Total of 253 girls, mean of 15.6 (0.05) years from 1st to 3rd grades of high school participated in this 6-month school-based cluster randomized controlled trial. "Healthy Habits, Healthy Girls-Brazil (H3G-Brazil)", originally developed in Australia, emphasized 10 key nutrition and physical activity (PA) messages delivered over 6 months. Disordered eating prevention procedures, i.e., prevention of weight-teasing, body satisfaction, and unhealthy weight control behavior, were added to the intervention. Body dissatisfaction, unhealthy weight control behaviors and social cognitive-related diet, and physical activity variables were assessed at baseline, immediate post-intervention, and 6-month post-intervention. Intervention effects were determined by one-way analysis of covariance or logistic regression, after checking for the clustering effects of school. The control group did not receive intervention prior to follow-up assessment. A conservative significance level was set at p < 0.01. RESULTS : Beneficial effects were detected for PA social support (F = 6.005, p = 0.01), and healthy eating strategies (F = 6.08, p = 0.01) immediate post-intervention; and healthy eating social support (F = 14.731, p = 0.00) and healthy eating strategies (F = 5.812, p = 0.01) at 6-month post-intervention. Intervention group was more likely to report unhealthy weight control behaviors (OR = 1.92, 95% CI 1.15-3.21, p = 0.01) at 6-month post-intervention. No other significant immediate or 6-month post effects were detected. CONCLUSIONS : H3G-Brazil demonstrated positive 6-month effects on some social cognitive variables but an adverse effect on unhealthy weight control behaviors. Thus, this study was not able to achieve synergy by combining obesity and disordered eating prevention procedures in an intervention among low-income girls in Brazil. BACKGROUND : Level I: cluster randomized controlled trial.