Purpose <p>Pediatric patients undergoing cardiac surgery are at risk of developing postoperative acute kidney injury (AKI). We hypothesized that a reduction in intraoperative renal (SrO₂) or cerebral (ScO₂) tissue oxygen saturation is associated with postoperative AKI.</p> Methods <p>We conducted a prospective observational study including fifty pediatric patients with non-cyanotic heart disease undergoing elective surgical repair with cardiopulmonary bypass. Intraoperative SrO₂ and ScO₂ were monitored using near-infrared spectroscopy (O3^® Regional Oximetry). Relative decreases of 10% and 20% from baseline SrO₂ and ScO₂ were analysed, calculating the total time below the threshold, area under the threshold, and time-weighted average. The primary outcome was the association between intraoperative SrO₂ and ScO₂ decreases, and the occurrence of postoperative AKI defined with the ‘Kidney Disease: Improving Global Outcomes’ criteria. Secondary outcomes included the association between other known or potential risk factors for AKI and postoperative AKI.</p> Results <p>The incidence of postoperative AKI was 18.4%. There was no association between the duration and extent of intraoperative reductions of SrO₂ and ScO₂ below 10% and 20% from baseline, and postoperative AKI (e.g., area under the threshold for ScO₂ decreases below 10%: 36.8 [11.8 to 419.9] % min in patients with AKI vs. 9.6 [0.6 to 92.8] % min in patients without AKI, <i>P</i> = 0.117). Preoperative serum creatinine, body mass index, intraoperative hypotension, and blood lactate were associated with postoperative AKI.</p> Conclusion <p>A decrease in intraoperative renal or cerebral tissue oxygen saturation was not associated with postoperative AKI in pediatric patients undergoing surgery for non-cyanotic congenital heart disease.</p>