Background <p>Postoperative delirium (POD) is a common and serious complication in elderly patients undergoing lower extremity orthopedic surgery, associated with increased morbidity and mortality. This study aims to evaluate the effect of intraoperative dexmedetomidine on POD incidence and severity in elderly orthopedic patients.</p> Methods <p>This prospective, single-center, randomized controlled trial enrolled patients aged ≥ 65 years scheduled for lower extremity orthopedic surgery under neuraxial anesthesia. Patients were randomly assigned to receive either dexmedetomidine (Group D) or placebo (Group C) in a 1:1 ratio. The primary outcome was the incidence of POD within 7 days postoperatively, assessed using the Confusion Assessment Method (CAM). Secondary outcomes included the severity of delirium, length of hospital stay, incidence of postoperative nausea and vomiting (PONV), postoperative visual analog scale (VAS) pain scores at 6&#xa0;h, 12&#xa0;h, 24&#xa0;h, and 48&#xa0;h, patient-controlled analgesia (PCA) usage, sufentanil consumption, and other adverse events.</p> Results <p>A total of 200 patients were randomized, with 92 in Group D and 91 in Group C completing the study. The incidence of POD was significantly lower in Group D (9.78%) compared to Group C (20.88%) (χ² = 4.35, <i>p</i> = 0.037). The severity of delirium was also lower in Group D (Z = -2.07, <i>p</i> = 0.038). There were no significant differences between groups in terms of PONV incidence (<i>p</i> = 0.641), VAS scores at any time point (all <i>p</i> &gt; 0.05), PCA usage (<i>p</i> = 0.532), sufentanil consumption (<i>p</i> = 0.591), or other adverse events (<i>p</i> &gt; 0.05).</p> Conclusion <p>Intraoperative dexmedetomidine infusion significantly reduces the incidence and severity of POD in elderly patients undergoing lower extremity orthopedic surgery. This intervention appears safe and effective, with no significant increase in adverse events or impact on postoperative pain management.</p>