Background: The Meta-Analysis Global Group in Chronic Heart Failure (MAGGIC) is a scoring system that is easy to use in outpatient clinics or at the bedside, and was developed to predict the survival of heart failure patients after hospitalization. Objectives: This study aims to evaluate the relationship between the MAGGIC score and cardiorenal syndrome (CRS) in patients with acute decompensated heart failure with reduced ejection fraction (HFrEF). Methods: This retrospective, single-center study, included 706 patients with New York Heart Association II-IV who were hospitalized and discharged for acute decompensated heart failure between 2016 and 2021. CRS type 1 was defined as acuteworsening of cardiac function leading to renal dysfunction. Patientswere divided into two groups: those with CRS and those without. The MAGGIC score of all patients was determined. The primary outcome was the occurrence of CRS. Results: CRS developed in 132 patients. The MAGGIC score was higher in CRS (+) patients compared to CRS (-) patients (30.70 8.09 vs. 23.96 5.59, p < 0.001). After amultivariable analysis,MAGGIC score [odds ratio (OR): 3.92, p < 0.001], sodium (OR: 0.92, p = 0.003), N terminal pro B type natriuretic peptide (OR: 1.78, p = 0.009), hs troponin (OR: 1.28, p = 0.044),MRA (OR: 0.61, p = 0.019) and furosemide dose (OR: 1.03, p = 0.001)were found to be independent predictors of CRS development. The MAGGIC score was associated with CRS development (area under curve = 0.778). Conclusions: The MAGGIC score may be associated with CRS in HFrEF patients.