This study examined whether adolescents' social aggression is socialized through exposure to peers' socially aggressive text messaging. Using data on the socially aggressive content of text messages that 221 participants (Mage = 15.02 years; 46.7% female) sent to and received from peers, and teacher ratings of participants' in-person social aggression, this study found that exposure to peers' socially aggressive texting about out-dyad peers predicted positive changes in adolescents' text-based and in-person social aggression. Gender differences were examined, and results were mixed. In ninth grade, girls sent more socially aggressive text messages than boys; however, by 10th grade, these differences disappeared. Gender differences in adolescents' in-person social aggression and their exposure to peers' socially aggressive texting were nonsignificant at both time points. There was no evidence of gender differences in the links between exposure to peers' socially aggressive texting and adolescents' socially aggressive texting. However, marginal differences were found in the associations between exposure to peers' socially aggressive texting and adolescents' in-person social aggression. Results suggest that texting provides an additional platform for peer socialization of adolescents' social aggression. (PsycINFO Database Record (c) 2019 APA, all rights reserved).