Contrast-induced nephropathy (CIN) is associated with worse prognosis in patients with acute coronary syndrome (ACS). Early identification and intervention for patients with a high risk of CIN are very important to improve clinical outcomes. Inflammation plays important role in the development of CIN in the setting of ACS. The monocyte to high-density lipoprotein ratio (MHR) is a novel inflammatory marker. Bleeding is also associated with worse prognosis in such patients. We aimed to investigate whether the preprocedural MHR had a predictive role for CIN development in such patients. In addition, using the thrombolysis in myocardial infarction classification, we aimed to assess whether there was any relationship between bleeding and CIN. A total of 647 patients (496 males; age: 63.3 ± 12.7 years) with ACS who underwent percutaneous coronary intervention (PCI) were included in the study. Seventy patients (10.8%) had developed CIN. Age, diabetes mellitus, contrast volume, estimated glomerular filtration rate, and MHR were independent predictors for CIN. Preprocedural MHR may be used as a simple marker of CIN. It may help with the early identification of patients with ACS who underwent PCI who are at high risk of CIN thus allowing the planning of protective measures.