The vast majority of patients with congenital heart disease (CHD) survive into adulthood, but many face lifelong complications, which often result in a hospital admission. The increasing number of hospitalizations in adults with CHD (ACHD) poses a significant challenge for healthcare systems globally, especially as heart failure (HF) is becoming increasingly common in this population and is the leading cause of morbidity and mortality. Besides HF, other major contributors to this increase in admission volume are hospitalizations related to mild lesions, comorbidities and pregnancies. Ιn-hospital mortality ranges between 0.8 and 6.1%, while hospitalizations related to HF predict medium-term mortality in ACHD population. Understanding the predictors of hospitalization and in-hospital mortality is, therefore, important for ACHD healthcare providers, who should identify patients at risk that require escalation of treatment and/or close monitoring. This article reviews the available literature on hospitalization patterns in ACHD patients, with a focus on HF-related hospital admissions and specific diagnostic subgroups.