This meta-analysis examined the direct (primary) and collateral (secondary) effects of peer tutoring on social and behavioral outcomes for 128 participants in prekindergarten through grade 12 across 20 studies using SCR designs. The overall TauU weighted effect size across studies was 0.62 (95% CI [0.58, 0.66]), indicating that a small to moderate effect on behavioral and social outcomes can be attributed to peer tutoring. Moderator analyses indicated that cross-age tutoring, peer tutoring interventions that did not use reward contingencies, and interventions that measured direct effects yielded higher effect sizes. The direct effect of peer tutoring on behavioral and social outcomes was moderately large (ES 0.75), whereas the collateral effect was relatively small (ES 0.43). Furthermore, peer tutoring had a greater effect on improving social skills and social interactions (ES 0.69) and reducing disruptive and off-task behaviors (ES 0.60) than academic engagement (ES 0.38).