The purpose of this synthesis is to summarize the effectiveness of peer-mediated interventions on the mathematics performance of both students with disabilities and those at risk for mathematics disabilities. Meta-analytic techniques were used to calculate mean effect sizes for 17 studies that met inclusion criteria. Results indicate that peer-mediated interventions in mathematics are moderately effective for improving students' mathematics performance. Also, findings are strongest for students at risk for mathematics disabilities, elementary-aged participants, and mathematics computation content. Recommendations for future research and practical implications are discussed.