This study aimed to investigate associations between reactive and proactive aggression and peer relations and peer deviance among high school girls. A total of 442 high school students participated in this study. Reactive–Proactive Aggression Questionnaire, the Peer Relations Scale, and the Peer Deviance Scale were used to collect data. Results revealed that self-disclosure, loyalty, mild deviance, and serious deviance were significantly and positively correlated with both reactive and proactive aggression. Findings also indicated that self-disclosure, loyalty, and mild deviance among peers were significant predictors of reactive aggression, while loyalty and mild deviance were significant predictors of proactive aggression.