The clinical value of increased levels of neutrophil gelatinase-associated lipocalin (NGAL) in patients with septic acute kidney injury (AKI) is still unclear. This study aimed to assess the link between illness severity and NGAL in patients with septic AKI.This is a retrospective observational study that took place at the Fourth Hospital of Hebei Medical University, Shijiazhuang, China. The cohort included 365 patients who were admitted to the ICU during the 21-month period. Of them, 18 patients were diagnosed with sepsis (septic group). The average age of patients in the septic group was over 65, and 60.00% of them eventually progressed to septic AKI. Plasma NGAL (pNGAL) and urine NGAL (uNGAL) levels at defined time points were measured. AKI staging was done based on the Kidney Disease Improving Global Outcomes (KDIGO) classification. The Sequential Organ Failure Assessment (SOFA) and Acute Physiology and Chronic Health Evaluation (APACHE) II scores were determined. Patterns and associations between NGAL levels with SOFA scores and different stages of septic AKI were investigated.Both pNGAL and uNGAL showed a positive correlation with SOFA and proved to be reliable predictors of the same. Furthermore, the accuracy of severe sepsis (SOFA ≥ 8) was 0.67 for pNGAL and 0.66 for uNGAL. Real-time detection of pNGAL and uNGAL indicated that they were good biomarkers of severe septic AKI. Area under the receiver operating characteristic (AUROC) for pNGAL and uNGAL were 0.72 (0.69-0.85), and 0.83 (0.71-0.95), respectively. However, only patients with KDIGO 3 AKI presented significantly elevated levels of pNGAL (p < 0.05). Furthermore, the uNGAL level at each stage of septic AKI was higher than that of the non-AKI period (p < 0.01).In patients with septic AKI, levels of NGAL correlated with SOFA. Levels of pNGAL were good predictors of severe kidney injury and uNGAL levels could detect mild stages of AKI.