Objective To evaluate the effects of intensive care unit (ICU)-acquired hypernatremia (IAH) on the outcome of septic shock patients. Methods This retrospective study analyzed 116 septic shock patients admitted to the ICU of the First Affiliated Hospital of Soochow University from August 2018 to December 2022. Patients were divided into two groups: IAH group and normonatremia group. χ2 test, t test and the Mann-Whitney U test of the non-parametric test were used to compare the differences in clinical data between the two groups. Independent risk factors for IAH were identified by unconditioned Logistic regression analysis, and receiver operating characteristic (ROC) curves were constructed to determine their role in predicting IAH. The Kaplan-Meier curve was used to evaluate the effects of IAH and its duration on 28-day survival. Results Renal insufficiency, K+ concentration, body temperature max, mechanical ventilation, chronic critical illness, rapid recovery, sepsis-associated encephalopathy, persistent inflammation, immunosuppression and catabolism syndrome, and the length of stay in ICU had significant differences (P<0.05). Multivariate logistic regression analysis showed: total urine volume in the previous 3 days [odds ratio (OR) 1.09, 95% confidence interval (CI) 1.01 - 1.16, P=0.019] and sodium content in enteral nutrition preparations (670 mg) (OR 6.00, 95%CI 1.61 - 22.42, P=0.006) were independent risk factors for IAH. In addition, the area under the ROC curve of total urine output in the first 3 days was 0.800 (95%CI 0.678 - 0.922, P=0.001). Finally, the duration of IAH was significantly correlated with 28-day survival rate (P=0.020). Conclusions IAH is a common and serious complication in septic shock, and is the main cause of poor prognosis. Sodium status may act as an ideal screening tool for patients with septic shock.