Perioperative neurocognitive disorders (PNDs) are frequent and severe complications in older surgical patients, encompassing postoperative delirium, delayed neurocognitive recovery, postoperative neurocognitive disorder, and long-term cognitive impairment. These complications lead to prolonged hospital stay, elevated medical expenditure, and compromised long-term quality of life. In this 2026 narrative review, we systematically outline up-to-date evidence on the pathophysiology, risk factors, screening approaches, and evidence-based interventions for PNDs. The core mechanisms involve neuroinflammation, gut microbiota dysbiosis, blood–brain barrier disruption, cerebral hypoperfusion, oxidative stress, and tau hyperphosphorylation. Key risk factors include advanced age, preoperative cognitive impairment or frailty, intraoperative hypotension, deep anesthesia, hypothermia, cardiopulmonary bypass, and suboptimal postoperative pain and sleep control. Bedside tools (Mini-Cog, MoCA, MMSE, FRAIL scale) permit feasible risk stratification; tau-PT217, NfL, S100A12, and GFAP are emerging predictive biomarkers. Dexmedetomidine is a pharmacologic agent that has been extensively studied and has relatively strong supporting evidence. Non-pharmacological interventions and multidisciplinary care are recommended as first-line strategies. Outstanding issues include optimal intraoperative hemodynamic and anesthetic thresholds, causal links between delirium and long-term cognitive decline, and clinical validation of biomarkers. Future research demands large-scale multicenter randomized controlled trials and standardized workflows to strengthen personalized perioperative brain protection in elderly surgical patients.