BackgroundThe World Cancer Research Fund/American Institute for Cancer Research Cancer Prevention Recommendations are lifestyle-based guidelines that aim to reduce cancer risk. A systematic review and meta-analysis of studies investigating associations between a score for adherence to the 2018 Cancer Prevention Recommendations and cancer risk was conducted. MethodsMEDLINE, Embase, Web of Science, and Scopus were searched for studies published to November 28, 2022. In meta-analysis, the estimated risk ratios and 95% CIs for adherence score as a continuous (per 1-point increment) and categorical (highest vs. lowest score category) variable using random-effects models were estimated. ResultsEighteen studies (11 cohort; seven case-control) were included investigating incidence of breast (n = 7), colorectal (n = 5), prostate (n = 2), lung (n = 2), pancreatic (n = 1), endometrial (n = 1), unknown primary cancer (n = 1), chronic lymphocytic leukemia (n = 1), and overall (any) cancer (n = 1). The summary risk ratio per 1-point increment in adherence score was 0.89 (95% CI, 0.85-0.93; I-2 = 76.5%; n = 7) for breast cancer, 0.88 (95% CI, 0.84-0.91; I-2 = 26.2%; n = 4) for colorectal cancer, and 0.92 (95% CI, 0.86-0.98, I-2 = 66.0%; n = 2) for lung cancer. There were no significant associations with prostate or other cancers. Meta-analysis results using categorical adherence score variables were consistent with these findings. ConclusionsGreater adherence to the 2018 World Cancer Research Fund/American Institute for Cancer Research Cancer Prevention Recommendations was associated with lower risk of breast, colorectal, and lung cancers. Future studies investigating associations with risk of other forms of cancer are warranted. PROSPERO registration numberCRD42022313327.