Obstructive sleep apnea (OSA) is an established risk factor for high blood pressure (BP) in adults. However, it remains unclear whether the same association could be found in children and adolescents. Therefore, we conducted a systematic review and meta-analysis of observational studies to evaluate the associations between childhood OSA and BP outcomes. The review protocol was registered in PROSPERO (CRD42021225683). We performed a systematic literature search to identify relevant cross-sectional and longitudinal studies up to July 6, 2021. Of the 4902 identified articles, a total of 12 cross-sectional studies and 2 cohort studies were included in the final analyses. In the cross-sectional analyses, the mean systolic BP (SBP) were significantly higher in children with mild or moderate-to-severe OSA compared to the healthy controls, and these effects were more pronounced during the nighttime. In prospective studies, moderate-to-severe childhood OSA was associated with a risk of elevated SBP in adulthood (Mean difference = 4.02 mm Hg, 95% CI = 1.32 to 6.72). Taken together, our results suggest that moderate-to-severe childhood OSA is associated with a higher risk of adverse SBP outcomes. Early detection and treatment of OSA may promote cardiovascular health in children and adolescents and possibly in future adulthood.