Interventions that address adolescent conduct problems are essential for decreasing negative risk behaviors and promoting positive protective factors among youth. Although interventions have been developed and tested in the United States, preventive evidence-based interventions (EBIs) are less available in Latin American countries such as Ecuador. Therefore, the purpose of this study was to evaluate the efficacy of an evidence-based, parent-centered intervention,Familias Unidas, in preventing/reducing conduct problems, across time, among youth in Guayaquil, Ecuador. Ecuadorian youth (ages 12 through 14) and their respective primary caregiver were recruited from two public schools and randomized to either Familias Unidas or Community Practice. A series of latent growth models were run to test for differences between Familias Unidas and Community Practice on conduct disorder symptoms across three timepoints covering 6 months. Ecuadorian mental health professionals were trained to deliver the evidence-based intervention. Findings indicate no direct relationship between condition and average change in conduct problems at 6 months post baseline. However, indirect effects favoring Familias Unidas over Community Practice were found through improvements in family functioning. Findings highlight that Familias Unidas was efficacious in an international setting and indicate the viability of successfully delivering preventive EBIs in Ecuador.