Background: Septic acute kidney injury (AKI), identified when sepsis and AKI present concurrently, is a syndrome of acute function impairment and organ damage, which accounts for similar to 50% AKI in the intensive care unit (ICU). Methods: This study retrospectively reviewed 591 patients who were diagnosed with sepsis and admitted to the ICU of Beijing Friendship Hospital from January 2009 to December 2014. According to the concentration of serum sodium, the 591 patients were further divided into 3 groups: normal group, hyponatremia group, and hypernatremia group. Results: The arterial partial pressure of carbon dioxide (PaCO2, P=0.014), concentration of sodium (Na+, P<0.001), and chloride ion (Cl-, P<0.001), blood urea nitrogen (BUN, P<0.001), acute physiology and chronic health evaluation (APACHE) score (P<0.001), sequential organ failure assessment (SOFA) score (P<0.001), and Glasgow score (P<0.001) showed significant differences. The SOFA score [P=0.040; odds ratio (OR)=1.261], body mass index (BMI, P=0.041; OR=1.229), P content (P=0.032; OR=7.180) and creatine kinase myocardial band (CK-MB, P=0.006; OR=1.168) may be risk factors for occurrence of AKI in patients with hypernatremia. The AKI (P<0.001; OR=6.850) and P content (P=0.027; OR=3.676) may be risk factors for death in patients with hypernatremia. The Na+ suggested a predictive ability for AKI (P<0.001; area under the curve (AUC): 0.586) but not for death (P=0.104). Conclusions: Hypernatremia is independently associated with an increased risk and has a predictive ability of AKI in patients with sepsis.