Ultra-processed foods (UPFs) constitute an increasing proportion of modern diets and may contribute to the development and progression of chronic kidney disease (CKD). This review summarizes current evidence linking UPF consumption with adverse kidney outcomes and discusses the underlying pathophysiological mechanisms. UPFs are typically high in sodium, added sugars, unhealthy fats and food additives, while being low in dietary fiber and essential micronutrients. Their consumption may promote inflammation and oxidative stress, metabolic acidosis, hypertension, gut microbiota dysbiosis, insulin resistance, and metabolic syndrome. Epidemiological studies consistently associate higher UPF intake with an increased risk of incident CKD, an accelerated decline in the estimated glomerular filtration rate, CKD progression and unfavorable cardiovascular and mortality outcomes. Reducing UPF intake and replacing these products with minimally processed plant-based foods may therefore represent a practical dietary strategy for kidney protection. However, most available evidence is observational, and further prospective and interventional studies are required to establish causality and define CKD-specific dietary recommendations.