Chronic inflammation is implicated in breast cancer (BrCa) development; however, studies on the association of the inflammatory potential of diet and breast cancer have produced conflicting results. With this as background, we investigated the association between dietary inflammatory index (DII®) scores and BrCa risk in an Iranian case-control study. In this study, 136 newly diagnosed breast cancer patients and 272 hospitalized controls were recruited using convenience sampling. DII scores were computed from dietary intake data collected through a validated food frequency questionnaire (FFQ). Adjusted odds ratios (OR) and 95% confidence intervals (CI) for the association between the DII and BrCa risk were estimated by logistic regression. After controlling for multiple potential confounders, a significantly increased BrCa odds was observed in the highest quartile of DII score compared to the lowest quartile (ORquartile 4 vs. 1 = 2.64, 95% CI: 1.12-6.25; Ptrend = 0.01). In subanalysis based on menopausal status, a positive association was observed between the DII and BrCa risk among premenopausal women (ORquartile 4 vs. 1 = 5.51, 95% CI: 1.45-20.93; Ptrend = 0.005); however, no association was detected in postmenopausal women. Our findings suggest that more proinflammatory diets, indicated by higher DII scores, may increase the odds of BrCa, especially among premenopausal women.