We aimed to examine whether anthropometric indices, dietary factors, and nutrient intakes of women with and without breast cancer (BrCa) are associated with the oxidative balance score (OBS). This case-control study was carried out among 253 patients with BrCa and 267 healthy subjects aged >18 years. The OBS was calculated by using the following 13 dietary and non-dietary anti- and prooxidant components: dietary antioxidants (selenium, fiber, β-carotene, vitamin D, vitamin C, vitamin E, and folate), dietary prooxidants (iron and saturated and polyunsaturated fatty acids), and nondietary anti- (physical activity) and prooxidants (smoking and obesity). The binary logistic regression was used to determine the association OBS with BrCa. After adjusting for potential confounders in the final model, there was evidence that the odds of BrCa decreased with increasing categories of the OBS (OR = 0.53, 95% CI 0.28 - 0.98; P-trend = 0.021). When we made stratified analysis by menopausal status, OBS was inversely associated with odds of BrCa in premenopausal women after adjusting for potential confounders. No significant association was found between OBS and odds of BrCa among post-menopausal women. Our data suggest that OBS scores were associated with decreased BrCa risk in the overall population.