Social media engagement has become a critical part of adolescent social interactions, making it important to examine individual differences in motivations for social media engagement as well as associated adjustment outcomes. Additionally, much of the extant research focuses on how much time adolescents spend on social media; researchers have only recently begun to differentiate specific social media behaviors and their varied role in adolescent development (e.g., Valkenberg & Peter, 2011). Based on recent research, I investigated four social media behaviors: self-disclosure, self-presentation, lurking, and social monitoring, along with social media engagement in terms of time and frequency. Based on hormonal activation theory (Forbes & Dahl, 2010), I focused on pubertal and social goal correlates of individual differences in social media engagement among adolescents. I also examined positive (prosocial support) and negative (peer victimization, internalizing problems) adjustment associated with social media engagement. Participants were 426 public school students (54.2% female, 73.6% Caucasian, mean age = 12.91, SD = .92) from sixth (N = 152), seventh (N = 142), and eighth (N = 132) grades who completed self-reported survey measures during their Health classes. Adolescents used more passive (lurking, social monitoring) than active social media (self-disclosure, self-presentation) behaviors. Girls reported more social media engagement than boys, and older adolescents reported more social media engagement than younger adolescents. Pubertal timing was not associated with social media engagement; instead, social goals (i.e., popularity goals and preference goals) were strongly associated with adolescents’ social media use. Social media engagement was reliably associated with adolescent adjustment. Self-presentation may function as a double-edged sword, promoting peer prosocial support but also increasing the risk for peer victimization and internalizing problems. Self-disclosure was uniquely associated with an increased risk of peer victimization, and lurking was uniquely associated with internalizing problems. Social monitoring was not uniquely associated with any of the adjustment outcomes. Contrary to previous literature (e.g., Kross et al., 2013), the amount of time spent on social media was not uniquely associated with any adjustment outcomes after social media behaviors were controlled, suggesting the importance of examining what adolescents are doing with that time. Unexpectedly, the frequency of social media use (a measure less often considered in the literature) appeared to be uniquely associated with more adaptive adjustment. The association between social media engagement and adjustment was stronger for girls than for boys (particularly for peer victimization). Findings extend previous research demonstrating the importance of considering specific social media behaviors in adolescent development. Future research should longitudinally examine the role of social media engagement on adolescent adjustment. Additionally, multi-method approaches (e.g., observational data collection, peer nominations) should be utilized to better understand the role of social media engagement on adolescent development. Finally, future research should examine different social media platforms (e.g., Twitter, Fortnite, Snapchat) and adolescent adjustment. / Psychology