Background <p>The potential association between dietary inflammatory index (DII) and colorectal cancer (CRC) risk, as well as colorectal adenomas (CRA) risk, has been extensively studied, but the findings remain inconclusive. We conducted this systematic review and dose-response meta-analysis to investigate the relationship between the DII and CRC and CRA.</p> Methods <p>We comprehensively searched the PubMed, Embase, Cochrane Library, and Web of Science databases for cohort and case-control studies reporting the relationship between DII and CRA, or between DII and CRC, as of 15 July 2025. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using a random-effects model. Dose-response analysis was conducted where possible. Subgroup analyses were conducted to account for possible sources of heterogeneity. Funnel plot, Egger’s test, and Begg’s test were utilized to assess publication bias.</p> Results <p>Twenty-two studies were included, involving 7,612 CRA patients, 25,359 CRC patients, and 896,592 controls. The pooled ORs for CRC and CRA in total population comparing the highest DII to the lowest DII were 1.61 (95% CI, 1.42–1.83) and 1.19 (95% CI, 0.96–1.47), respectively. The pooled ORs for CRC and CRA per unit increase in DII were 1.14 (95% CI, 1.08–1.20) and 1.19 (95% CI, 1.03–1.38), respectively. Stratification by sex revealed a positive association between DII and CRC risk in both males and females. However, this association was stronger in males (Highest DII vs. lowest DII: OR = 1.67, 95% CI [1.39, 2.00]) (Continues DII: OR = 1.16, 95%CI [1.06, 1.26]). Dose-response analysis revealed a nonlinear positive correlation between CRC risk and DII (P _{for non−linearity} &lt; 0.0001).</p> Conclusions <p>Our findings suggest that dietary habits characterized by a high inflammatory index may increase the risk of CRA and CRC.</p> Trial&#xa0;registration <p>PROSPERO registration number: CRD42025641934.</p>