The Monocyte to high density lipoprotein ratio (MHR) has been postulated as a novel parameter associated with adverse renal and cardiovascular outcomes. In this study we investigated the association of MHR with cardiac surgery-associated acute kidney injury (CSA-AKI).In this retrospective study, we analyzed the data pertaining to 1505 patients undergoing cardiopulmonary bypass (CPB) surgery. The CSA-AKI, which was defined using Kidney Disease Improving Global Outcomes criteria. Concurrently, a retrospective scan of patient files was conducted and information relevant to nephropathy such as the level of their serum creatinine (SCr), Blood urea nitrogen (BUN), uric acid (UA), serum cystatin C (Cys-C), total cholesterol (TC), triglycerides (TG), glucose and MHR, ejection fraction, CPB duration time, and other indicators.About 1505 patients were studied of whom 195 developed AKI. MHR was significantly higher in the AKI patients (p = 0.001). In multivariate logistic regression analysis, MHR, UA, Cys-C, age, glucose, and history of chronic kidney disease or hypertension were independently correlated with CSA-AKI.As a laboratory index, the elevated MHR is convenient, independent, and a useful predictor for CSA-AKI.