Aims: Hospitalization for acute decompensated heart failure (HF) is associated with poor outcome. As specific data for Belgium are currently not available, the aim of the Belgian BIO-HF registry is to evaluate the clinical characteristics, in-hospital mortality and outcomes after discharge of patients hospitalized for acute HF. Methods and results: This is a prospective observational cohort study conducted in 2 Belgian hospitals. For the current analysis, the first 904 patients who were enrolled between 2008 and 2012 were selected for assessment of clinical characteristics and short-term outcome (all-cause mortality and all-cause mortality + rehospitalization 3 months after discharge). Mean age of patients was 77 years (51% ≥ 80 years), 44% were women and 64% had an eGFR < 60 ml/min/m2. Mean LVEF was 42% with only 40% with LVEF ≤ 35%, 20% with LVEF between 36 and 49% and 40% with LVEF ≥ 50%. In-hospital mortality was 7.1% with a mortality of 22% in the subgroup of patients with a creatinine ≥ 2 mg/dl and systolic blood pressure ≤ 110 mmHg on admission. Three months after discharge, the all-cause mortality rate was 7.6% and the all-cause mortality or hospitalization for HF 18.3%. Multivariate Cox regression analysis revealed eGFR, COPD, absence of beta blockers and atrial fibrillation at discharge (all P < 0.05) as independent predictors of all-cause mortality. Conclusions: In this Belgian registry of mainly elderly patients admitted with acute HF, a relatively preserved EF and a reduced kidney function were present in the majority of patients. In-hospital and short-term mortality after discharge remain high and are mainly related to the presence of co-morbidities such as renal failure and COPD. Co-morbidities should be the focus for future efforts to improve the dire outcome of these patients.