In this chapter, we highlight how a relationship-based intervention (PeerLearning.net) can reduce peer victimization. Peerlearning.net is a software program that aids teachers in the delivery of cooperative learning (CL) lessons, a form of small-group instruction that creates conditions under which students are motivated and reinforced to work cooperatively with one another while they are learning. CL has been studied for decades, with significant benefits documented in areas of academics, peer relationships, and behavioral and mental health for youth. Recent intervention studies highlight the promise of CL in reducing peer victimization and bullying for youth. Despite promising data, CL is not routinely used for school-wide bullying prevention. In this chapter, we argue that CL should be viewed as a viable intervention for reducing peer victimization. Additionally, the design of CL offers several advantages for helping more vulnerable groups of students (e.g., adolescent victims, chronically victimized youth, youth experiencing identity-based victimization) as well as practical advantages for implementation in school settings when compared to traditional curriculum-based bullying prevention programs. © Jun Sung Hong, Heng Choon (Oliver) Chan, Annis Lai Chu FUNG and Jungup Lee 2024. All rights reserved.