Bullying is a prevalent problem in schools and is linked to negative mental health and academic outcomes. Latinx youth, specifically, may experience higher rates of bullying and depression than their non-Latinx peers. Considering that bullying often occurs in front of peers, bystander intervention can be an effective way to reduce bullying at school and lower associated negative outcomes. However, most bullying bystander intervention research does not focus on Latinx students. This study applied the Bullying Literature Project—a five-session bullying intervention that uses existing children’s books—to promote bystander behavior among Latinx elementary school students. The present study examined the effectiveness of the Bullying Literature Project intervention on bystander behaviors using a quasi-experimental design among 192 elementary school students (44.3% females, 81 third graders, and 111 fourth graders) from eight classrooms in two schools with majority low-SES, Latinx student bodies. Results showed that students in the intervention group reported significant increases in positive bystander behaviors compared with students in the waitlist control group (F(1, 166) = 4.72, p = .031). Social validity data suggested that teachers and students were satisfied with the intervention. We discuss practical implications for the use of children’s literature by school-based mental health providers as a medium for bystander intervention to promote positive bystander behaviors among elementary school students.