Abstract: Researchers have found that blended learning, combining face-to-face and online learning, can improve student outcomes. However, there is a paucity of research that examines how blended learning in teacher professional development impacts student achievement. The purpose of this meta-analysis is to analyze the impact of blended learning teacher professional development on mathematics and science achievement of PreK-12 students. We have used robust variance estimation techniques to detect any effect the blended learning professional development might have. Additionally, we have examined how technology used in professional development might moderate student achievement. We found a small positive effect of blended teacher professional development on student achievement. Moderator analysis revealed surface level use of technology in professional development yielded a small positive effect on student achievement. Implications for blended learning in professional development are discussed.