Background: Inflammation is important in chronic disease and can be modulated by dietary exposures. Our aim was to examine whether the inflammatory potential of diet after cancer diagnosis, assessed using the dietary inflammatory index (DII), is associated with all-cause and cause-specific mortality among women diagnosed with invasive breast cancer in the Women’s Health Initiative (WHI).Methods: Our analytic cohort included 2,150 postmenopausal women, ages 50 to 79 years at baseline, who developed invasive breast cancer during follow-up and completed a food frequency questionnaire (FFQ) on average 1.5 years after diagnosis. Women were followed from breast cancer diagnosis until death or the end of follow-up by October 2014. Energy-adjusted DII (E-DII) scores were calculated from food plus supplements using a nutrient-density approach. Cox proportional hazards models were fit to estimate multivariable-adjusted HRs and 95% confidence intervals (CIs) for all-cause, breast cancer-specific, and cardiovascular disease (CVD) mortality.Results: After a median 13.3 years of follow-up, 580 deaths from any cause occurred, including 212 breast cancer deaths and 103 CVD deaths. Lower (i.e., more anti-inflammatory) E-DII scores were associated with a lower risk of CVD mortality (HRQ1VSQ4 = 0.44; 95% CI, 0.24-0.82; Ptrend = 0.005), but not with breast cancer-specific mortality (HRQ1VSQ4 = 0.96; 95% CI, 0.62-1.49; Ptrend = 0.96) or all-cause mortality (HRQ1VSQ4 = 0.82; 95% CI, 0.63-1.05; Ptrend = 0.17).Conclusions: Consuming a more anti-inflammatory diet after breast cancer diagnosis may be a means for reducing risk of death from CVD.Impact: Survival after invasive breast cancer diagnosis may be improved by consumption of an anti-inflammatory diet. Cancer Epidemiol Biomarkers Prev; 27(4); 454-63. ©2018 AACR.