Introduction: Childhood aggression is a major health problem throughout the world, particularly in recent years. Aggression in the preschool years, when the child starts extensive interaction with age group, becomes an important issue. The reason for problem could be attributed to a set of biologic, psychological, cultural, and familial variables. Objective: This study aimed to determine the level of aggression and socioeconomic factors associated with aggression in preschool children in Rasht city. Methods: This cross-sectional descriptive analytical study was conducted among preschool children in Rasht city in 2013.Study samples included 614 children aging 5 to 7 years who were chosen by two-stage cluster sampling from preschool centers affiliated to Education and Welfare departments in Rasht. Data collection tool included two questionnaires, Preschool Children Aggression Scale completed by teachers to evaluate verbal, physical aggression, relationship and impulsive anger of children and questionnaire of related socioeconomic factors, completed by parents. Then data were analyzed by using descriptive and analytical statistics (Kruscal Wallis, Mann Whitney U and Multiple Linear Regression Test). Results: The mean aggression score was in the area of verbal aggression 4.5 ± 7.5, physical aggression 2.3 ± 4.3, relationship 4.5 ± 6.3, impulsive anger 4.5 ±5.7 and total aggression score 15.8 ± 20.8. There was a statistically significant relation between location change of stressful events and relationship aggression (p<0.02), computer games and area of the physical aggressive (p<0.01) and overall aggression (p<0.03), housing type and area of verbal aggression (p<0.02), relational aggression (p<0.007), impulsive anger (p<0.01) and overall aggression (p<0.008), median family income and the area of relational (p<0.05). The results of regression showed that children living in villas have 4.8 degrees score of aggression higher than children living in apartments (CI95%:0.7-8.9). The results of the study also showed that the median family income was considered as other predictor of aggression in children and as the income category defined by Division of Subsidized organizations increased one level, aggression score decreased an average of 3 units {(CI95%:-5.9- (-0.01)}. Conclusion: According to the results of the study it seems that socioeconomic factors are the main predictors of aggression in children, especially in the area of relational aggression and impulsive anger. Therefore, to prevent aggression in children, special attention must be paid to these factors