The purpose of this study was to examine the effects of adapted peer tutoring (APT) on social interactions and early language and literacy skills of pre-school-age children who were English language learners (ELLs). APT was the treatment for this study. Quasi-experimental group comparison design was applied. Two inclusive pre-school classrooms were randomly assigned as the experimental group and two other classrooms were assigned as the comparison group. A total of 75 children participated in this study. The ELLs from the experimental group demonstrated significant improvement than their peers from the comparison group in positive social interaction behaviour, receptive language, and print knowledge. The total effect indicated that children's social interaction behaviour moderately mediated the APT effectiveness on language acquisition. (author abstract)