In people with prediabetes, the importance of regression to normal glucose regulation is increasingly appreciated. Meta-analyses of clinical trials have shown that vitamin D lowers the risk of progression from prediabetes to diabetes; however, there is less known about whether vitamin D promotes regression to normal glucose regulation. We did a systematic review and meta-analysis of clinical trials that tested vitamin D vs. placebo among patients with prediabetes and reported on the regression to normal glucose regulation outcomes. We searched Medline (through PubMed), Embase, and the trial registry ClinicalTrials.gov for randomized, placebo-controlled trials of at least 6 months’ duration that reported on the effects of oral vitamin D vs. placebo on normal glucose regulation in adults with prediabetes. We extracted trial characteristics and the primary outcome, regression from prediabetes to Normal Glucose Regulation, as defined by each trial. The search identified 10 eligible trials. The baseline characteristics of the study cohorts were: mean age range 20-74 years old, mean BMI range 24-38 kg/m2, mean blood 25-OH-D concentration range 12-28 ng/mL, median study duration 1.25 (range 0.5-5) years. Across trials, 416/2253 (18.5%) participants in the vitamin D groups reached normal glucose regulation vs. 312/2225 (14.0%) participants in the placebo group. All studies favored vitamin D, with relative risks ranging from 1.09 to 2.05 (excluding a highly imprecise outlier). The summary relative risk of regression to normal glucose regulation for vitamin D treatment vs placebo was 1.27 (95% CI 1.12-1.45), with no heterogeneity (I2 = 1%). No participant-level variables were collected, limiting meaningful subgroup analyses. We conclude that in adults with prediabetes, vitamin D increases the likelihood of regression from prediabetes to normal glucose regulation.