Short QT syndrome (SQTS) is a primary electrical disease associated with atrial fibrillation and sudden cardiac death (SCD). The long-term prognosis in young patients has not been reported. The aim of this study was to define the clinical characteristics and long-term outcome of pediatric patients with SQTS. This is an international case series involving 15 centers. Patients were analyzed for Gollob score, ECG characteristics, genetics, clinical events, and efficacy of medical/ICD therapy. To assess the prognostic value of Gollob scoring we devised a modified Gollob score that excludes clinical events from the original scorecard. Twenty-five patients <21 years old at clinical presentation [84% males; median (IQR) age: 15 (9) years] were followed for 5.9 (2.7) years. Symptoms occurred in 14 of 25 patients (56%), including aborted SCD in 6 and syncope in 4. QTc range was 194–355 ms (mean ± SD: 304 ± 41). Arrhythmias were common: atrial fibrillation (4), ventricular fibrillation (6), supraventricular tachycardia (SVT; 1), and polymorphic ventricular tachycardia (1). No differences were found in ECG parameters (QT, QTc, J point-Tpeak. and early repolarization) between asymptomatic and symptomatic patients. Sixteen patients (84%) had a familial or personal history of cardiac arrest. A gene mutation was identified in 5 of 21 (24%) probands: KCNH2 (2), KCNJ2 (2), and KCNQ1 (1). Symptomatic patients had a higher median modified Gollob score compared with asymptomatic patients (5.0 ± 1.0 vs 4.0 ± 1.0, P = .044). Those with a score <5 remained event-free, except for an isolated episode of SVT, over an average 6-year follow-up. Quinidine was used alone or in conjunction with other antiarrhythmic agents in 9 patients. Eleven of 25 index cases underwent ICD implantation. Two patients had therapeutic ICD shocks. A high incidence of inappropriate ICD shocks was observed, affecting more than two thirds of ICD recipients. SQTS is associated with a high risk of aborted SCD and arrhythmias among the pediatric population. Asymptomatic patients with a modified Gollob score <5 remained event-free, except for an isolated episode of SVT over an average 6-year follow-up. Young SQTS patients have a high rate of inappropriate ICD shocks.