BACKGROUND: The oxidative balance score (OBS) has been utilized to assess the overall pro- and antioxidant exposure status in various chronic diseases. The current meta-analysis was carried out to pool the association between OBS and the risk of cancer. METHODS: We systematically searched the Web of Science, PubMed, Scopus, Embase, and Google Scholar up to August 2023. All observational studies which evaluated the association of OBS with the risk of cancers were included. There was no time of publication or language restrictions. Heterogeneity between studies was assessed using the Chi-square-based Q-test and the I. A random-effects model meta-analysis was conducted to estimate the pooled effect sizes. Possible sources of heterogeneity were explored by subgroup and meta-regression analysis. RESULTS: Totally, 15 studies (9 case-control and 6 cohorts) were eligible for meta-analysis. Random effect model meta-analysis of case-control studies showed that higher OBS significantly decreases the odds of cancers (pooled OR: 0.64, 95% CI: 0.54, 0.74). In the cohort studies, the association of OBS with the risk of cancers was not significant (pooled HR: 0.97, 95% CI: 0.80,1.18). The subgroup analysis showed that cancer type and gender were the potential sources of heterogeneity. CONCLUSION: Our results show an inverse and significant association between higher OBS and odds of colorectal cancers in case-control and cohort studies. In the case of prostate cancer in cohort studies, our results did not align with the hypothesis. Considering the importance of diet and antioxidant balance in the conditions of malignancy, it is suggested to conduct more comprehensive studies with standard measurement methods to obtain conclusive results.