Introduction: This study aims to investigate effectiveness of teaching management skills on decreasing aggression among third grade high school boy-students in Ilam city.
 
Materials & Methods: This is a semi-experimental study with an unequal control group design. The statistical population of this study consisted of all the high school boy-students in Ilam city (western Iran). In our research, the Ahvaz's aggression questionnaire was used to determine the aggression level among the participants. A total of 40 students were chosen using multistage cluster sampling. In order to assign individuals to the groups, 30 students with high aggressiveness score were selected and randomly assigned to two experimental and control groups. Then, the experimental group participated in a cognitive-behavioral aggression management training course for 10 sessions of 90 minutes; however, the control group did not receive any training.
 
Findings: The results indicated that teaching aggression management skills was effective in reducing aggression. There was a significant difference between the experimental and control groups in the post-test scores for the aggression variable with the pre-test control scores at P <0.0001 level.
 
Discussion & Conclusions: Our findings suggest that aggression management training is effective in promoting aggression control and improving students' helpful attributions; thus, the students can learn the principles of rational and emotional behavior theory through such a program.