The increasing survival to adulthood of patients with congenital heart disease (CHD) has changed the epidemiology of adult CHD (ACHD) patients and has led to an increment in hospitalization rates due to heart failure (HF). ACHD patients hospitalized for HF have a five-fold higher risk of death than those compensated. HF occurs predominantly in patients with tetralogy of Fallot, single ventricles, and after the Mustard operation for transposition of the great arteries. Diagnostic strategies applied in acquired HF patients are usually used to evaluate ACHD patients, but sometimes this can postpone the identification of HF that can become manifest with unusual and peculiar signs or symptoms. In the same way, therapeutic management resembles the acquired HF one, even if no large randomized clinical trials have been conducted in ACHD patients. Therefore, a close monitoring in dedicated units is mandatory in order to identify in time HF manifestations and manage them adequately.