The aim of this research was to examine the correlation between sociodemographic characteristics, emotional intelligence, empathy and certain aspects of temperament with aggressiveness in adolescents, as well as sex differences in aggressiveness. We examined which variables have a significant contribution in explaining aggressiveness. The research was conducted in two high schools (191 high school students and 177 vocational school students), and a total of 368 respondents (M = 204, F = 164) in the age range from 15 to 18 years old (M = 16.17, SD = 0.83). The obtained results suggest that adolescents with lower emotional intelligence have higher scores on defiance and confrontation, and those adolescents with a lower ability to regulate and manage emotions show higher scores on overall aggressiveness and the subscales of treatment and defiance and confrontation. Adolescents with lower empathy report higher scores on the treatment and bully subscales. Adolescents with low self-control report higher overall aggressiveness, but also on the subscales of defiance and confrontation and treatment. Adolescents with higher overall aggressiveness, as well as with higher scores on the subscales of defiance and confrontation and victimization, also have a more expressed negative affect. Furthermore, boys show more aggressive behavior compared to girls when aggressiveness is viewed as a total score and the treatment, victim, and bully subscales. Vocational school students show higher levels of aggressiveness compared to high school students when aggressiveness is measured as a total result and on the subscales treatment, victim and bully. Five models were tested with which we examined the contribution of predictors in the explanation of aggressiveness. Criterion variables were aggressive behavior and itssubscales. The model with which we explained the highest percentage of variance, 27.7%, is the one in which the criterion variable is the aggressiveness subscale of defiance and confrontation. According to this model, adolescents with lower self-control, more expressed negative affect, weaker ability to regulate and manage emotions will more often show aggressive behavior. The obtained results have significant implications for practical work in the context of strengthening self-control, empathy and abilities of emotional intelligence.