We assessed the frequency and implications of a history of syncope of up to 1 year prior to hospitalization with acute heart failure (AHF) between February and November 2012. Data were collected for 5005 patients hospitalized with AHF and analyzed and compared according to the absence/presence of a history of syncope (group 1 vs group 2). Prior syncope among patients with heart failure was 5.3%. Age, gender, hypertension, atrial fibrillation, bundle branch block, left ventricular ejection fraction (LVEF), and obstructed coronary vessels were comparable in the 2 groups. Group 2 patients were more likely to smoke or have diabetes mellitus, stroke, and cardiac arrest. Group 2 patients frequently required aggressive treatment and had more worse in-hospital and 1-year outcomes compared to group 1. After adjustment for age, sex, ethnicity, and LVEF, multivariate regression analysis showed that history of syncope predicted in-hospital mortality (odds ratio: 2.61; 95% confidence interval: 1.707-4.002). History of syncope during the year prior to the index admission with AHF is a marker of worse outcomes regardless of patient age and LVEF. Further studies are required to confirm this observation and its clinical implications.