Students' prosocial behavior is linked to their own and their classmate's engagement in the classroom. This raises the question of through what pathway prosocial behavior is linked to engagement. This study investigates whether early adolescents' peer belonging mediates the relationship between prosocial behavior and classroom engagement. The potential moderation effect on gender was also investigated due to gender differences that favor girls. Participants were 679 middle school students from rural, low-income communities in the Midwestern United States (51% girls, 49% boys; M[subscript age]= 12.65, SD = 1.09). Students completed self-report surveys in the spring of 2022. Structural equation modeling (SEM) was used to test the main effect of students' perceptions of their own and their classmates' prosocial behavior on peer belonging and emotional, behavioral, and cognitive engagement, and the mediating effect of peer belonging on engagement. Results suggest that students' perceptions of their own and their classmates' prosocial behavior were positively linked to their emotional, behavioral, and cognitive engagement. Additionally, these relationships were mediated by peer belonging for emotional and behavioral (but not cognitive) engagement. These findings were robust across gender. Findings have implications for classroom-based intervention. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]