Peers are critical to defending and bystanding during episodes of bullying. This study investigates the extent to which friends can shape defending and bystanding as well as social cognitions associated with these two behaviors (i.e., perceptions of self-efficacy and moral distress). The study sample consisted of n = 1354 early and middle adolescents (7th‒10th grade; 81.4% Italian; 51.3% boys) in northern Italy. Employing a longitudinal social network analytic approach, using stochastic actor-oriented modeling, this study found that adolescents become more similar or stay similar to their friends in both behaviors and perceptions, with no clear indication that students select friends based on similar levels of behaviors or perceptions. The findings illustrate how defending and bystanding behaviors and related social cognitions are developed within friend (peer) networks.