Peer tutoring is an instructional strategy that allows students to help one another learn content material through the repetition of key concepts. In more than 40 years of published studies, literature reviews, and meta-analyses of peer tutoring, this quantitative synthesis of the literature is the first to examine the impact of peer tutoring on academic, social, and linguistic outcomes for English language learner (ELL) students. A total of 363 ELLs in kindergarten through 12th grade are represented in the analyses across 17 studies; seven studies used single-case research designs, nine used group designs, and one was a case study. Findings suggest that ELLs benefit from peer tutoring academically, socially, and linguistically. Implications for research and practice are discussed.