Background and purpose: Children’s and adolescents’ mental and physical health have great importance in every society important, and enable them to perform their social roles competently. Therefore, identifying the influencing factors which affect this major population has been one of the important issues for psychologists in recent decades. The purpose of this study was to examine the relationship between children’s family cohesion and aggression.

Results: present study was a descriptive research. The study population consisted of all the fifth-grade female elementary school students who were studying in the schools of Sari City in 1393-94 academic year. Sample consisted of 254 students who were selected using random multistage cluster sampling method. Data were collected using Samani family cohesion questionnaire (1381) and Shahim Aggression Questionnaire for children (1385).

Findings: findings showed a significant negative correlation between family cohesion with the dimensions of physical aggression, relationship aggression, reactive aggression, and total aggression (p = 0.001). Results of regression analysis showed that about 17 percent of the variance in aggression can be explained by family cohesion.

Conclusion: According to our findings, coherent families encourage their children to think about the outcomes of their behaviors. Thus, the children of these families are more likely to internalize moral codes.