This study investigated the effectiveness of a program to promote civic responsibility and prevent antisocial behavior in a sample of Italian adolescents. Participants were 83 Italian male adolescents, attending the second year of high school (Mean age = 15.79; SD = 0.87). In order to test the efficacy of different strategies (in-classroom training and service activity in a voluntary organization) we divided students into two experimental groups—one classroom of students participated in both strategies (training + volunteering group) and another classroom only participated in the training (training only group)—and one control group. Process and efficacy evaluations were completed. Data were collected before and following the intervention. The process evaluation revealed that the program was highly accepted and appreciated by students. The efficacy evaluation revealed no intervention effects on civic responsibility. However, the training + volunteering group reported a significant decrease in antisocial behavior after the program. Thus, the program was effective in preventing antisocial behavior but not in promoting civic responsibility in our sample.