Cancer survivors consuming the highest amounts of ultra-processed foods faced a 48% increased risk of death from any cause and 57% higher cancer-specific mortality compared to those eating the least, based on 14.6 years of follow-up data from 802 Italian participants. The relationship persisted even after accounting for overall Mediterranean diet quality, suggesting ultra-processed foods carry independent health risks beyond simply displacing nutritious options. Inflammatory biomarkers and elevated resting heart rate explained approximately 40% of this mortality association, pointing to chronic inflammation and cardiovascular stress as key mechanistic pathways. This represents crucial evidence extending ultra-processed food research into vulnerable populations. While previous studies have linked these foods to increased disease risk in healthy individuals, demonstrating harm specifically among cancer survivors—who already face compromised immune function and heightened inflammation—underscores the urgency of dietary interventions in oncology care. The finding challenges the common clinical focus solely on maintaining caloric intake during and after cancer treatment, suggesting food quality may be equally critical for long-term survival outcomes.