Objective: The aim of the present study is to examine the factors related to Aggression in Iranian and Indian school children. Method: Attachment security (dependency, availability, and total) was considered as the variable. The KSS questionnaire was administrated for 600 students in the 5th grade; 300 were Iranian and 300 were Indian (each consisted of 150 boys and 150 girls).Results: Attachment security demonstrated significant negative correlations with Aggression in the boys, girls and the total Iranian sample. The girls’ dependency on mothers was the only case with insignificant correlation. In the Indian sample, attachment security was also found to be significantly negatively correlated with Aggression. The only exception was the correlation between mother’s availability and Aggression in girls, which was not significant Conclusion: It is important that parents treat their children in a tender, loving manner so that a secure attachment develop between them.