Background: Vitamin K antagonists (VKAs) may have potential antitumor effects in prostate cancer. However, the findings ofobservational studies are inconsistent. The purpose of the present study was to estimate the quantitative association between VKAsuse and prostate cancer risk by combining the results of all eligible observational studies.Methods: PubMed and Web of Science database were searched from inception until May, 2018. A DerSimonian random-effectsmodel was used to combine the studies. Study heterogeneity was measured using the chi-squared and I2statistics.Results: Six eligible studies were eventually included in our meta-analysis. There was an inverse but not statistically significantassociation between ever use of VKAs and the risk of prostate cancer (relative risk [RR] 0.84, 95% confidence interval [CI] 0.70–1.01,P=.063) with large heterogeneity across studies (P<.001 for heterogeneity, I2=94.6%). When analysis restricted to long term ofVKAs user (>3 years), the pooled risk estimate was 0.83 (0.77–0.90) without obvious heterogeneity (P=.597, I2=0.0%).Conclusion: This meta-analysis indicates that VKAs use may be associated with a decreased risk of prostate cancer, especially inlong-term users.Abbreviations: CI =confidence interval, NOS =Newcastle-Ottawa Scale, OR =odds ratio, RR =relative risk, VKAs =vitamin Kantagonists.Keywords: meta-analysis, prostate cancer, risk, vitamin K antagonist