The present study tested the feasibility, appropriateness, and efficacy of a preventive intervention to reduce risk factors for substance use and delinquency among youth in juvenile justice diversionary settings by promoting positive youth development and building personal strengths and prosocial relationships. Participants in the study (N = 288) were predominantly male (69%) and in the 9th grade (14 years old) or higher (91%), received the preventive intervention, and completed confidential questionnaires at the pre-test and post-test. The majority of youth who participated in the intervention rated the program topics (77.9%) and activities (72%) as appropriate for their age, would recommend it to their peers (73.6%), and would use the skills learned in the future (85.4%). Comparison of post-test adjusted means revealed that the prevention program had a significant positive impact on key knowledge, attitudes, and skills including goal-setting, stress-management, and communication skills.