The literature on the association between reading comprehension and mathematics skills is complicated and conflicting. This study seeks to illuminate the nature of the association between mathematics skills and reading comprehension by incorporating potential moderators, namely components of mathematics skills, domains of content standards in mathematics, age, language status, and developmental issues. The dataset for this study included 49 studies with 91 correlation coefficients representing 37.654 participants. The findings obtained in this study showed that reading comprehension had a significantly strong effect on students' mathematics skills. This association was moderated by components of mathematics skills, domains of content standards in mathematics, age, language status, and developmental issues. Moderation analyses revealed that problem-solving was the strongest moderator of the association between reading comprehension and mathematics skills, whereas spatial skills were the weakest moderator of this relationship. Based on domains of content standards in mathematics, geometry was the weakest moderator of the association between mathematics skills and reading comprehension. Moreover, the effects of reading comprehension on students' mathematics skills significantly differed in favor of elementary students, students with learning disabilities, and second language learners. Therefore, this research can shed light on the literature by synthesizing the effects of reading comprehension on students' mathematics skills.