BACKGROUND The purpose of this study was to determine the association of the neutrophil-to-lymphocyte ratio (NLR) measured at the time of admission to intensive unit (ICU) with acute kidney injury (AKI) in patients with sepsis and septic shock. In addition, we investigated whether the NLR affects in-hospital mortality in septic AKI patients. METHODS In this retrospective study, a total of 222 adult patients with sepsis and septic shock were included, who were admitted to the ICU of Zhongnan Hospital of Wuhan University from January 2015 to December 2017. Sepsis and septic shock were diagnosed based on sepsis-3 consensus. AKI was diagnosed according to the KDIGO-AKI criteria. The primary outcome of the study was septic AKI. The secondary endpoint was in-hospital mortality of patients with septic AKI. RESULTS 132 patients (59.46%) had AKI, and 64 (28.83%) died, of whom 55 (41.67%) in the AKI group and 9 (10.00%) in the non-AKI group. The NLR of the AKI group was significantly higher than that of the non-AKI group, and there was a statistically significant difference between the two groups (P < 0.001). Multivariate logistic regression analysis suggested that the NLR was independent predictors of septic AKI (OR = 1.047, 95% CI: 1.005-1.091, P = 0.026). The ROC curve showed that the AUC of the NLR for predicting septic AKI was 0.656 (95% CI 0.584-0.728, P < 0.001) and the cutoff value was 17.11 (sensitivity, 62.1%; specificity, 68.9%). However, no correlation was found between the NLR and in-hospital mortality in septic AKI patients. CONCLUSIONS NLR, a laboratory variable that is simple, widely available and inexpensive, was associated with the development of septic AKI and may be potential for risk stratification of septic AKI.