In the current study, the relationships between aggression, self-compassion and sleep quality of high school students have been examined. 529 high school students (66% females and 34% males) participated in the study. Data were collected from participants through using a Pittsburgh Sleep Quality Index (PSQI), Aggression Questionnaire (AQ), Self-Compassion Scale (SCS), and Descriptive Questionnaire. The predictors of aggressiveness of the variables determined by simple correlation were investigated by multiple linear regression. According to the results, there was a positive and significant relationship between aggression levels and all sub-dimensions of self-compassion and sleep quality. In addition, it was observed that the levels of aggressiveness were significantly predicted by the sub-dimensions of self-compassion and sleep quality, and that the first three most effective predictive variables were over-identification, self-judgment and sleep quality.