Background: Galectin-3 (Gal-3) is a biomarker involved in a wide range of diseases including cardiac remodeling following acute myocardial infarction (AMI). Identification of prognostic markers in patients with AMI can guide strategies towards improved survival and the quality of life. Methods: Our study included 59 patients with AMI and preserved ejection fraction. We determined the Gal-3 plasma concentration within 24 hours of chest pain onset from aortic root, femoral/radial artery, coronary sinus and cubital vein. Major adverse cardiovascular events (MACE) were evaluated at six months follow-up. Results: MACE at six months post-AMI was recorded in 20 patients (34%). The Gal-3 plasma concentration from aortic root and the femoral/radial artery were independent predictors of MACE at six months follow-up after the first AMI (OR 1.228; 95%CI: 1.011-1.491; p=0.038; OR 3.438; 95%CI: 1.275-9.265; p=0.015). ROC analysis identifies the Gal-3 plasma concentration from aortic root as a better predictor of MACE or death (cut-off >10.86 ng/ml; AUC 0.858; 95%CI: 0.744-0.973; p<0.001) than Gal-3 plasma concentration from femoral/radial artery (cut-off >10.18 ng/ml; AUC 0.742; 95%CI: 0.596-0.888; p=0.006). Conclusion: The Gal-3 plasma concentration in patients with AMI determined during coronary angiography, especially from the aortic root, within 24 hours after chest pain onset is a valuable biomarker of prognosis at six months follow-up.