Background: "Strong Families" is a family program aimed at preventing risk behaviors in adolescents from 10 to 14 years of age. It has been developed by the Pan American Health Organization (PAHO/WHO) and is based on the Iowa Strengthening Families Program. This program has been certified and has been proven to effectively prevent adolescent drug and alcohol abuse in several countries around the globe. Aim: To evaluate the Strong Families Program toward adjusting current parenting styles, aiming to decrease risk behaviors in Chilean adolescents. Material and Methods: A quasi-experimental study involving 120 families, selected from 6 schools within the Metropolitan Region of Santiago, Chile. A group of 129 adolescents and 124 parents were chosen by convenience to be intervened. A control group of 223 adolescents and 165 parents were not intervened. The families that underwent intervention attended to 7 educational sessions. The intervened and control groups were evaluated before intervention as well as 6 months after intervention, by means of self-administered evaluation tools. Results: The intervened parents showed significant parenting changes six months after intervention, which resulted in less yelling (p = 0.007), insults (p = 0.002) and lack of control when their children misbehaved (p = 0.008). Regarding the risk behaviors in the intervened and control adolescents, no changes were observed in terms of the consumption rate of tobacco, alcohol or illegal drug use, or in sexual risk behaviors. Conclusions: After six months of intervention, the Program proved to be effective in modifying parenting styles. However, no changes were observed in risk behaviors among adolescents, which could occur within a longer period of time, as reported in other studies. (Rev Med Chile 2012; 140: 726-731).