:Background:Aggression is the most significant psychopathological risk factor. It is a multifaceted construct and can affect students’ social, mental and physical health. The present study was conducted to investigate factors associated with aggression among elementary school girls and boys using the theoretical framework of Social Cognitive Theory in Kermanshah city, Iran.Methods:The cross-sectional study was conducted on 900 students, including 445 girls and 455 boys, 563 parents and 104 elementary school teachers in the fourth, fifth and sixth educational grades in Kermanshah city in 2018. The proportionate stratified random sampling was used. The Adolescent Peer Relations Instrument (APRI) was used to measure aggression. To measure the variables of social cognitive theory, a researcher-made questionnaire was used. Data analysis was conducted using descriptive and inferential statistics via the SPSS software.Results:It was showed that 29% and 10% of the students had moderate and high levels of aggression, respectively. Also, 30.6% of them were moderate victims and 45.6% were intense victims. Self-efficacy (p less than 0.001), perceived social norms (p=0.011), observational learning (p less than 0.001), outcome expectations (p=0.027), outcome expectancies (p=0.028) and per-ceived situational (p less than 0.001) were reported as the significant predictors of aggressive behaviors in the students based on the Social Cognitive Theory constructs. In total, they explained for 37.3% of changes in aggressive behaviors. Parents’ knowledge (p=0.005), parents’ attitude (p=0.012), teachers’ attitude (p less than 0.001), and teachers’ self-efficacy (p=0.021) had statistically significant relationships with aggression in the students.Conclusions:Aggression among children and adolescents is getting alarmingly prevalent. The Social Cogni-tive Theory is the appropriate framework for the prediction of aggression behaviors in children and adolescents. Therefore, designing and implementing educational interventions based on this theory can help with the management of aggression in children and adolescents.