This study examined direct and indirect forms of peer socialization of nonsuicidal self-injury (NSSI) in adolescent friendship networks. Data were collected among 348 adolescents (55% females; Mage = 15.02 years; SD = 0.53) at four assessment waves. Stochastic actor-based models revealed no evidence for direct socialization of NSSI: adolescents whose friends reported higher NSSI did not increase their NSSI over time. However, indirect forms of socialization were found. After controlling for direct socialization and selection effects, friends' depressive symptoms predicted changes in male and female adolescents' NSSI, and friends' impulsivity predicted changes in male adolescents' NSSI. Findings highlight the importance of extending peer influence research beyond the classical “modeling” paradigm by providing evidence that peers may indirectly socialize adolescents' NSSI.