The purpose of the study was to implement "we can resolve our conflicts" training program to elementary school students and to assess the effectiveness of this school-based conflict resolution training program, designed to enhance students' conflict resolution skills and social competence and consequently decrease aggression. Three hundred and ninety-four elementary school students participated in the study. The training group consisted of 327 students and the control group consisted of 67 students. A pretest-posttest control group design was used. The training students received the conflict resolution training two times a week in 40 min sessions over a 10-week period. The conflict resolution training program included empathy, anger management, social problem solving, and cooperative conflict resolution skills. Before and after the training, both training and control groups were assessed in terms of their conflict resolution skills, social competence, and reactive and proactive aggression levels. Results indicated that the conflict resolution training increased students' constructive conflict resolution skills and social competence and consequently decreased reactive and proactive aggression levels.