The construct of emotional intelligence is defined as “the ability to perceive accurately, appraise, and express emotion; the ability to access and/or generate feelings when they facilitate thought; the ability to understand emotion and emotional knowledge; and the ability to regulate emotions to promote emotional and intellectual growth” (Mayer and Salovey, 1997). Furthermore, human aggression is any behavior directed toward another individual that is carried out with the proximate (immediate) intent to cause harm. In addition, the perpetrator must believe that the behavior will harm the target, and that the target is motivated to avoid the behavior (Anderson and Bushman, 2002). Garcia-Sancho et al. (2014) through a systematic review, found strong evidence to suggest that emotional intelligence and aggressive behavior are negatively related. Eighteen of the nineteen identified studies revealed that people with high EI showed less aggressive behaviors than those with low emotional intelligence, this relationship being consistent across age, gender, and culture. The present study aimed to investigate the relationship between emotional intelligence and aggressive behavior and to examine gender differences in emotional intelligence of upper elementary school boys and girls. The study included 186 participants, ranging in age from 12 to 15 years, using the Emotional Competence Questionnaire, the Emotional Comprehension Test, and the Aggression Scale for Children and Adolescents. The analysis of the findings revealed a significant negative correlation between emotional intelligence measures and measures of aggressive behavior at the group level and in boys and girls groups, while gender differences were found for the emotional intelligence measure related to emotion understanding (girls scored higher), to naming and expressing (boys were more competent) and on noticing and understanding emotions (girls were more competent).