This study examined the effectiveness of the First Step to Success (FSS) early intervention program for preventing antisocial behavior in Turkey. Participants included 24 students, their teachers and parents from four K-8 elementary schools. The experimental group included 12 targeted students (four kindergarten, four first-grade and four second-grade students) who received the intervention. Both quantitative and qualitative methods were carried out by using a pre-posttest experimental design. Results indicated that there were significant decreases in problem behaviors and significant increases in social skills and academic competence of targeted students. In addition, teachers and parents reported significant positive changes in problem behaviors and social skills of their children. Most teachers and parents were highly satisfied with the program. Limitations of the study and directions for future research are discussed. (Contains 3 tables and 1 figure.)