Preventing antisocial behaviors appearing at an early age-before they become chronic-through effective early intervention programs, has become an important issue in recent years. In Turkey, the increase in the number of children at risk of antisocial behavior makes it necessary to get these behaviors under control at an early age through some effective and systematic programs. Nevertheless, in Turkey, the number of studies on this subject is limited. Therefore, this study aims to explore the effectiveness of the preschool version of the First Step to Success (FSS) early intervention program on antisocial behaviors and social skills of Turkish children aged 36-72 months, who are at risk of antisocial behaviors. The study comprises a pretest-posttest experimental design with a control group. At the end of the study, the total problem and externalized problem behaviors of children in the experimental group decreased significantly. However, the program implementation did not result in a significant difference between experimental and control groups in terms of social skills. Regarding social validity findings, the majority of teachers and parents were happy with the program.