Objectives: This study examined the effects of middle school students emotional intelligence on their aggressiveness and interpersonal relationships. Methods: Data were collected by questionnaires from 316 middle school students in Daegu city. To analyze the sample survey data, descriptive statistics, t-test, ANOVA, pearson correlation coefficient and simple regression analysis were performed with SPSS/PC 18.0 program. Results: First, among the general characteristic differences, academic achievement and economic status yielded a significant difference in emotional intelligence. Gender, economic status, and educational background produced a significant difference in aggressiveness, while gender, academic achievement, and economic status showed a significant difference in interpersonal relationships. Second, an examination of the correlation among emotional intelligence, aggressiveness, and interpersonal relationships found that the higher the emotional intelligence, the lower the aggressive, and the higher the interpersonal relationships. Third, general characters and emotional intelligence explain 22% of agressiveness. Gender, age, economic status, and emotional intelligence have a significant influence on agressiveness. Fourth, the general characters and emontional intelligence explain 45,5% of interpersonal relationships. The economic status and emotional intelligence have a significant influence on the interpersonal relationship. Conclusion: Based on the results, the study is of great importance, in that it provides the basis for future studies, which can be used to help school teachers and students' parents understand the importance of adolescents emotional intelligence and promote the students' quality school life.