Objective <p>The primary goal was to investigate whether the presence of preoperative lacunar infarcts (LACI) was associated with postoperative delirium (POD) in elderly patients undergoing elective major abdominal surgery.</p> Design <p>A prospective cohort study.</p> Setting and participants <p>Patients aged ≥ 65&#xa0;years from a tertiary level A hospital in China.</p> Methods <p>The POD was assessed once daily within the first postoperative 3&#xa0;days using the Confusion Assessment Method. Neurocognitive tests using the Mini-mental State Examination (MMSE) and the Beijing version of the Montreal Cognitive Assessment scales were carried out within 3&#xa0;days before surgery and 4–7&#xa0;days after surgery. Regional cerebral oxygen saturation (rScO₂) was recorded in the operating room. Logistic regression analysis was used to evaluate the impact of preoperative LACI on POD and to explore the risk factors for POD.</p> Results <p>A total of 369 participants were analyzed, 161 in the preoperative LACI-positive group (P group), and 208 in the preoperative LACI-negative group (N group), respectively. The incidence of POD was 32.7% in our study. The incidence of POD was significantly higher in the P group than in the N group (39.1 vs 27.9%, risk ratio, 1.66; 95% CI 1.07–2.58; <i>P</i> = 0.022). Furthermore, the P group exhibited lower mean rScO₂ values during the procedure (<i>P</i> &lt; 0.001). In exploratory analysis, the advanced age (<i>P</i> = 0.005), sex (<i>P</i> = 0.038), and lower preoperative MMSE score (<i>P</i> = 0.019) were independent risk factors for POD in patients undergoing major abdominal surgery.</p> Conclusions and implications <p>Preoperative LACI was common, and constituted a risk factor for POD in older patients undergoing abdominal surgery. Despite the frequent subclinical nature, the preoperative LACI led to lower mean rScO₂ during the procedure. These findings could help early identification of high-risk POD patients.</p>