In acute decompensated heart failure (HF), systemic venous congestion contributes to patients' symptoms and hospital admissions. The purpose of our study is to determine if venous congestion, examined using the venous excess ultrasound (VExUS) score, predicts HF-related hospitalization and mortality in patients admitted to the emergency department (ED) with acute decompensated HF. Fifty patients admitted for acute HF in ED underwent ultrasound (US) assessment according to the VExUS score within the first 24 and 72 h. All patients were followed up with a telephone call at 30 and 60 days after hospital discharge. On admission, 56% had a VExUS score of 3. After 72 h, 32% had no more signs of congestion at the Doppler VExUS examination (inferior vena cava < 2 cm, VExUS score of 0); a similar percentage still exhibited a VExUS score of 3 despite therapy. Eighty per cent of patients were hospitalized after admission to the ED, while six (15%) died in-hospital; all exhibited a first-assessment VExUS score of 3. No patient with a VExUS score < 3 died during the study. During short-term follow-up, 18 patients were readmitted to the ED for acute decompensated HF. Ninety-four per cent of the readmitted patients had a VExUS score of 3 at the Doppler assessment at the first ED admission. Severe venous congestion, defined as a VExUS score of 3 at the initial assessment of patients with acute decompensated HF, predicts inpatient mortality, HF-related death, and early readmission.