Disease‑related malnutrition is a significant global public health issue closely associated with perioperative complications and mortality rates. Postoperative delirium (POD) is a common complication of perioperative neurocognitive dysfunction following surgery. Relevant guidelines and clinical evidence support that nutritional risk/malnutrition is an important preoperative risk factor for POD. This article outlines the definitions and current status of nutritional risk/malnutrition and POD, reviews nutritional risk/malnutrition, nutritional support, nutrition‑related anthropometric indicators, nutrition‑related blood biomarkers, and the effect of micronutrient deficiencies and dehydration on POD. This review aims to provide references for improving the prevention and control of POD and enhancing the quality and safety of perioperative medical care.