This study examines the justification of aggressive acts in Uruguayan children and adolescents in different social situations as a function of age and sex, as well as the effect of differences in socioeconomic status on justification. A total of 663 participants aged 8 to 21 completed a self-report questionnaire designed to measure the justification of eight aggressive acts in six social situations. The results showed that adolescents justified both physical and verbal aggression more easily than children in a wide range of situations. As expected, boys justified physical aggression more easily than girls; however, no differences appeared in regard to verbal aggression. Unexpectedly, no statistically important differences were found in the justification of aggression related to the socioeconomic status of the participants. These findings are discussed in terms of previous studies from other cultures, in the hope of contributing to a deeper knowledge of the complex phenomenon of aggression.