This study employed a three-level meta-analytic approach to investigate the relationship between parental language input and children's language outcomes, as well as the moderating effects of relevant variables. The analysis incorporated 41 original studies, including 160 effect sizes, with a sample size of 5,563 children. Results from the random effects model indicated a significant, moderate positive correlation between parental language input and children's language outcomes. Moderator analysis demonstrated that the association between parental lexical diversity and child language outcomes was significantly stronger compared to sentence complexity. No significant moderating effects were found for variables such as child diagnosis, language, parent and child gender, language outcome measures, the context of data collection, study design and child age. The study discusses possible reasons for the discrepancies between these findings and those of previous research. Future studies should further explore moderating variables related to parental language input and children's language outcomes, with an increased focus on the impact of cultural, policy, and other social environmental factors to identify novel avenues for enhancing language development in children.