Background Preeclampsia is a severe pregnancy complication affecting 2–8% of pregnancies globally, contributing to substantial maternal and fetal morbidity and mortality. Vitamin D deficiency has been associated with an increased risk of preeclampsia, yet the efficacy of its supplementation during pregnancy in reducing preeclampsia incidence remains uncertain. Objectives This systematic review and meta-analysis aimed to evaluate the impact of vitamin D supplementation on the incidence of preeclampsia and related maternal and neonatal outcomes. Method We systematically searched PubMed, Scopus, Cochrane Library, and Web of Science until August 2024 for randomized controlled trials (RCTs) examining the effects of vitamin D supplementation on preeclampsia. Eligible studies included pregnant women with varying doses of vitamin D supplementation compared to placebo or standard care. Primary outcomes were the incidence of pre-eclampsia and preterm labor; secondary outcomes included serum 25-hydroxyvitamin D levels, low birth weight, and APGAR scores. Data were synthesized using R statistical software, with effect measures reported as relative risk (RR) and mean difference (MD) with a 95% confidence interval (CI). Results A total of 33 RCTs involving 10,613 participants were included. Vitamin D supplementation significantly reduced the risk of preeclampsia by 44.8% (RR = 0.55, 95% CI [0.43, 0.71], P < 0.0001) and preterm labor by 30% (RR = 0.70, 95% CI [0.51, 0.96], P = 0.0286). Subgroup analyses indicated that the benefits were more pronounced when the control group received a placebo rather than low-dose vitamin D. Serum 25-hydroxyvitamin D levels significantly increased in the supplementation group (MD = 32.42 nmol/L, 95% CI [20.33, 44.50], P < 0.0001). However, no significant differences were observed in the incidence of low birth weight (RR = 0.65, 95% CI [0.42, 1.02], P = 0.057) or Apgar scores at 5 min (MD = 0.20, 95% CI [-0.01, 0.40], P = 0.057). Conclusion Vitamin D supplementation during pregnancy significantly reduces the risk of preeclampsia and preterm labor, though its impact on neonatal outcomes remains unclear. These findings underscore the potential value of vitamin D supplementation in prenatal care for improving maternal outcomes. Further research is needed to clarify its effects on neonatal health.