Objective:To describe the complications associated with heart surgery, compare them to a reference population, and identify mortality risk factors. Patients and methods: Retrospective and descriptive study. All patients who underwent surgery at Hospital Garrahan in the 2013-2015 period were included. Age, weight, procedure, mechanical ventilation, length of stay in days, morbidity, and course were recorded. Renal failure requiring dialysis, neurological deficit, permanent pacemaker, circulatory support, phrenic nerve or vocal cord palsy, reoperation, wound infection, chylothorax, and tracheotomy were considered morbidities. A descriptive, statistical analysis by risk category was done using the Society of Thoracic Surgeons (STS) morbidity score. Results: 1536 patients, median age: 12 months (interquartile range [IQR] 25-75: 3-60), weight: 8 kg (IQR 25-75: 4.4 to 17.5), mortality: 5%. A total of 361 events were recorded in 183 patients. An unplanned reoperation was the most common event (7.2%); the rest occurred in ≤ 3% of patients. Compared to patients without complications, patients who had events required more days on mechanical ventilation: 9.95 ) versus 1.8 (IQR 2575: 1.46-2.14), p < 0.00001; a longer length of stay: 28.8 (IQR 25-75: 25.1-32.5) versus 8.5 (IQR 25-75: 7.9-9.2), p < 0.0001; and had a higher mortality: 19.6% versus 3.1% (RR: 4.58, 95% CI: 3.4 to 6.0), p < 0.0001. Circulatory support and renal failure were associated with a higher mortality. Conclusions: An unplanned reoperation was the most common event. Patients with complications required more days on mechanical ventilation and a longer length of stay and had a higher mortality. Circulatory support and renal failure were associated with a higher mortality.