Focusing on the variables that can affect both academic achievement and the well-being of students has been crucial for their development, making schools effective and designing educational policy as well as curriculum. The study has aimed to investigate the effect of peer bullying on academic achievement and to determine moderators in the relationship between these two terms by using TIMSS (The Trends in International Mathematics and Science Study) and PIRLS (Progress in International Reading Literacy Study) data through the meta-analysis method. Based on seven international survey data sets from TIMSS (2003, 2007, 2011, and 2015) and PIRLS (2006, 2011, and 2016), the current research has focused on 793 independent findings, including 3,503,005 students in 77 countries. In the analysis process, the mean effect size was measured by using the coefficient of standardized means (Cohen's d) based on the random effect model. In addition, the significance of the moderator variables was calculated by using the Q statistic. The findings of the study revealed that peer bullying had a significant effect on academic achievement, and in this effect, grades of the students and course types played moderator roles, while the culture of the countries was not a moderator. It could be concluded that the effect of peer relationships not only on the social development of students but also on their academic performance should not be ignored.