BACKGROUND: Significant advancements in treatment and care, as well as early detection, have contributed to an increase in cancer survival rates. Recently, the EAT-Lancet Commission on Food, Planet, Health proposed the "planetary health diet" but to date, no study has investigated the potential associations between adherence to the EAT-Lancet reference diet and mortality in cancer survivors. To determine whether higher adherence to the EAT-Lancet reference diet is associated with lower risk for all-cause, cancer, and cardiovascular mortality in cancer survivors. METHODS: Data from the prospective UK Biobank study were used. Information from UK Biobank's Touchscreen questionnaire was used to develop a score reflecting adherence to the EAT-Lancet reference diet. Cox proportional hazards regression was used to assess the association of the EAT-Lancet reference diet score with all-cause, cancer, and cardiovascular mortality in cancer survivors. RESULTS: Within 25,348 cancer survivors, better adherence to the EAT-Lancet reference diet was inversely related to all-cause mortality (hazard ratio (HR): 0.97, 95% confidence interval (CI): 0.95-0.99), 1 unit increase) and cancer mortality (HR: 0.98, 95% CI: 0.96-1.00), while mostly null associations were observed for major cardiovascular mortality (HR: 0.99, 95% CI: 0.95-1.03). CONCLUSIONS: Our findings suggest the adoption of the EAT-Lancet reference diet is associated with lower all-cause and cancer-specific mortality among cancer survivors.