Background: To assess whether intraoperative monitoring and intervention of regional cerebral oxygen saturation levels can reduce the incidence of postoperative cognitive dysfunction in patients undergoing cardiovascular surgery and contribute to patient prognosis. Methods: The Cochrane Library, PubMed, and the Web of Science were systematically searched for relevant randomized controlled trials involving the effects of cerebral oxygen saturation on the cognitive function of patients after cardiovascular surgery from January 1, 2000 to May 1, 2022. The primary outcome was the incidence of postoperative cognitive dysfunction. The secondary outcomes were length of hospital stay, length of intensive care unit (ICU) stay, length of mechanical ventilation, length of cardiopulmonary bypass, and other major postoperative outcomes such as renal failure, infection, arrhythmia, hospital mortality, and stroke. Data were pooled using the risk ratio or standardized mean difference with 95% confidence interval (CI). The original study protocol was registered prospectively with PROSPERO (CRD42020178068). Results: A total of 13 randomized controlled trials involving 1669 cardiovascular surgery patients were included. Compared with the control group, the risk of postoperative cognitive dysfunction was significantly lower in the intervention group (RR = 0.50; 95% CI: 0.30 to 0.85; p = 0.01; I{}^2 = 71%). The Duration of stay in intensive care units in the intervention group was also significantly shorter than that in the control group (standard mean difference (SMD) = –0.14; 95% CI: –0.26 to –0.01; p = 0.03; I{}^2 = 26%). Univariate meta-regression analyses showed that age is a major source of heterogeneity. Conclusions: Our current study suggests that intraoperative cerebral oxygen saturation monitoring and intervention can significantly reduce the incidence of postoperative cognitive dysfunction, and the length of intensive care unit stay after intervention is considerably reduced. Given that some limits in this review, more high-quality, and long-term trials are still needed to certify our findings.