Background: Inflammation plays a critical role in cardiac remodeling after myocardial infarction (MI). Monocyte to high-density lipoprotein-cholesterol (HDL-C) ratio (MHR) has emerged as a potential indicator of inflammation. Objectives: The study aimed to investigate the prognostic role of MHR at the time of hospital admission in late cardiac remodeling and subsequent 1-year mortality in an academic training and research hospital. Methods: This prospective multicenter study included 231 patients with acute ST-elevation MI. Left ventricular (LV) functions and volumes were assessed by cardiac magnetic resonance (CMR) imaging at 2 weeks and 6 months post-MI. The definition of adverse cardiac remodeling (AR) was based on the increase of LV end-diastolic volume by ≥ 12% at 6 months post-MI. All patients were followed for survival for 1 year after the second CMR imaging measurements. Results: At 6 months post-MI, 20 patients (23.8%) exhibited AR. The median MHR was higher in the AR group compared to the group without AR (2.2 vs. 1.5, p < 0.001). A positive correlation was found between MHR and infarct size in the groups with and without AR. High MHR was an independent predictor of AR (OR: 3.21, p = 0.002). The cut-off value of MHR in predicting AR was found to be >1.6 with 92.7% sensitivity and 70.1% specificity (AUC ± SE: 0.839 ± 0.03, p < 0.001). Mortality risk was 5.62-fold higher in the group with MHR of >1.6 (HR: 5.62, p < 0.001). Conclusions: These results indicate that admission MHR is a useful tool to predict patients with AR who are at risk of progression to heart failure and mortality after MI.