BackgroundThe positive youth development program highlights the abilities of adolescents and young people. This concept emphasizes that teenagers are capable of making positive changes (such as: flexibility, Responsibility, Identify abilities). This study aimed to determine the effectiveness of the Positive Youth Development (PYD) program on reducing aggression among high school female students in Yazd city. Iran.MethodsThis was a quasi-experimental study, using pretest-posttest design with a control group. In the 2019–2020 academic year, the statistical population comprised all female students in high school first and second years in the city of Yazd, Iran. Using purposive sampling and based on include and exclude criteria (high risk of aggression due to their scores on a screening test and Parental consent to participate in the class) 30 female students were selected. Randomly, they were assigned to an experimental(n = 15) and control groups(n-15). The Buss-Perry Aggression Questionnaire was conducted on students. The experimental group had 8 intervention sessions, whereas the control group received no intervention. The data were subsequently examined using Analysis of Covariance(ANCOVA).ResultsThe dependent t-test revealed a significant difference between the pretest-posttest aggression scores in the experimental group, but there was no significant difference in the control group. There was no significant difference in the mean scores of physical aggression, anger, and hostility in the experimental and control groups, but a significant difference was found between the experimental and control groups in the mean verbal aggression scores.Conclusiontraining of positive youth development did not affect on aggression and its three dimensions (physical aggression, anger, and hostility) and only affected adolescent verbal aggression.