Background <p>Acute respiratory infections (ARIs) remain a leading cause of morbidity and mortality in pediatric populations worldwide. Vitamin D has immunomodulatory functions that may influence susceptibility and outcomes of respiratory infections, yet trial results in pediatric populations remain inconsistent.</p> Methods <p>A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted in accordance with PRISMA guidelines. MEDLINE, Embase, Web of Science, and Cochrane Library were searched through April 2025. Eligible RCTs enrolled pediatric populations, comparing oral vitamin D supplementation with placebo or no treatment, and reported ARI-related outcomes. Pooled risk ratios (RRs) or mean differences (MDs) with 95% confidence intervals (CIs) were calculated using random- or fixed-effects models.</p> Results <p>Seventeen RCTs including 18,372 participants were analyzed. Overall, vitamin D supplementation did not significantly reduce ARI incidence (RR = 0.82, 95% CI: 0.64 to 1.06), hospitalization duration (MD = 0.03 days, 95% CI: -0.72 to 0.78), recovery time (MD = -4.36&#xa0;h, 95% CI: -11.87 to 3.15), or all-cause mortality (RR = 0.88, 95% CI: 0.60 to 1.28). Subgroup analysis showed preventive benefit with daily low-dose regimens (≤ 1000 IU/day; RR = 0.42, 95% CI: 0.27 to 0.66), but not with higher doses. Supplementation was associated with fewer serious adverse events (RR = 0.83, 95% CI: 0.71 to 0.96).</p> Conclusion <p>Vitamin D supplementation cannot be recommended as a universal intervention for childhood ARIs. Preventive efficacy may be achieved with daily low-dose regimens, but supplementation does not improve clinical outcomes once infection occurs. Vitamin D appears safe, and further high-quality pediatric trials are warranted to define optimal dosing strategies.</p> Trial registration <p>CRD420251133291.</p>