Abstract: Background: Acute Kidney Injury (AKI) is a notable postoperative complication in patients undergoing Coronary Artery Bypass Grafting (CABG). The Neutrophil-Lymphocyte Ratio (NLR) is an inflammatory marker that may be associated with postoperative AKI. This study aimed to evaluate the relationship between NLR and AKI in CABG patients at H. Adam Malik General Hospital Medan.