A metacognitive learner acts in a planful way, monitors their progress, flexibly adapts their strategies, and reflects on their learning. Unsurprisingly, a metacognitive approach to learning is an important predictor of children's academic performance and many attempts have been made to promote metacognition in young children. The current meta-analytic study evaluates the impact of such metacognition interventions on outcomes related to self-regulated learning and academic achievement in typically developing pre- and elementary school children. Structural, content-related, and methodological moderators were tested in this study including 349 effect sizes from 67 studies. An overall effectiveness of metacognition interventions was evidenced at immediate post-test g = 0.48 (95% CI [0.35, 0.61]), and at follow-up g = 0.29 (95% CI [0.17, 0.40]). Interestingly, metacognition interventions effectively enhanced children's self-efficacy only at follow-up, suggesting that the positive impact of these interventions can unfold over a protracted period. For the first time, children's executive functions were considered as outcome variables and results indicated a positive impact of metacognition interventions on these variables. One notable finding was that interventions that were delivered by teachers or task materials were more effective than interventions that were delivered by researchers for two outcomes related to self-regulated learning. This finding may reflect recent improvements in how teachers and researchers collaborate to develop intervention programs. The study supports and extends existing evidence that young learners benefit from metacognition interventions in myriad ways and provides novel insights relevant for pedagogical practice and theories of self-regulated learning.