Background: Open heart surgery using cardiopulmonary bypass (CPB) is considered one of the most frequent surgical procedures in which acute kidney injury (AKI) is a frequent and serious complication. The aim of the present study was to evaluate the efficiency of neutrophil gelatinase-associated lipocalin (NGAL) as an early AKI biomarker after CPB in cardiac surgery (CS). Methods: Thirty-seven adult patients undergoing CS with CPB were included in this retrospective study. They had normal preoperative renal function, as assessed by the creatinine (Cr) level, NGAL level, and estimated glomerular filtration rate. Serial evaluation of serum NGAL and Cr levels was performed before, immediately after, and 24 hours after the operation. Patients were divided into two groups: those who showed normal immediate postoperative serum NGAL levels (group A, n=30) and those who showed elevated immediate postoperative serum NGAL levels (group B, n=7). Statistical analysis was performed using Statistical Package for the Social Sciences version 18. Results: Of the 37 patients, 6 (6/37, 16.2%) were diagnosed with AKI. One patient belonged to group A (1/30, 3.3%), and 5 patients belonged to group B (5/7, 71.4%). Two patients in group B (2/7, 28.5%) required further renal replacement therapy. Death occurred in only 1 patient (1/37, 2.7%), who belonged to group B. Conclusion: The results of this study suggest that postoperative plasma NGAL levels can be used as an early biomarker for the detection of AKI following CS using CPB. Further studies with a larger sample size are needed to confirm our results.