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• Diet-related inflammation is increasingly related to female infertility. • Dietary inflammatory index (DII) and infertility have a non-linear correlation. • The risk of female infertility increases significantly when the DII ≥ 2.45. • Consumption of anti-inflammatory food may be beneficial for female infertility. Diet-related inflammation, which can be evaluated using the dietary inflammatory index (DII), is increasingly related to female infertility. However, studies on the association between DII and infertility are limited. In this study, we aim to explore the association between DII and infertility and its dose-effect relationship among women aged 20 to 45 years through a cross-sectional analysis of the National Health and Nutrition Examination Survey 2013–2018. A total of 2613 women aged 20 to 45 years were included and analyzed. The DII was calculated using the first 24-hour dietary recall interview data and divided into quartiles. Weighted multivariable logistic regression and restricted cubic spline analysis were used to explore the relationship between DII and infertility. The odds ratio (OR) (95% confidence interval [CI]) for the association between DII and infertility was 1.06 (0.96–1.19) after multivariable adjustment. Compared with the first quartile (anti-inflammatory diet), the fourth quartile of DII (pro-inflammatory diet) was more strongly associated with an increased risk of infertility, with an OR of 1.61 (95% CI, 1.05–2.47). Restricted cubic splines showed a J-shaped nonlinear association between DII and infertility (P for nonlinear =.003), with a cutoff point of 2.45. When DII was higher than 2.45, the OR for infertility was 1.95 (95% CI, 1.49–2.54). Similar results were observed among the subgroup analyses. In conclusion, this study found high DII (pro-inflammatory diet) increases the risk of female infertility. DII had a J-shaped nonlinear relationship with female infertility, whose cut point is 2.45. Controlling the intake of pro-inflammatory food may be beneficial for female infertility. This study included a total of 2613 women aged 20 to 45 years from the NHANES 2013–2018. The first 24-hour dietary recall interview data were used to calculate the dietary inflammatory index. A significant J-shaped nonlinear association between the dietary inflammatory index and infertility was found, whose cut point is 2.45 (P for nonlinear =.003). When the dietary inflammatory index was higher than 2.45, the risk of female infertility increased significantly. Abbreviation: NHANES, National Health and Nutrition Examination Survey. [Display omitted] [ABSTRACT FROM AUTHOR]