Background: Prognosis in patients with pediatric dilated cardiomyopathy (PDCM) is urgently required to identify high-risk patients. Elevated soluble ST2 (sST2) is associated with prognosis in adult patients with heart failure. This study aimed to assess the prognostic value of sST2 in PDCM. Methods: Ninety-four patients with PDCM were enrolled after admission from 2 centres in China and followed up for adverse events (death, cardiac transplantation, and heart-failure-related rehospitalization). B-type natriuretic peptide (BNP) and sST2 levels were measured. Results: Over a median of 678 (interquartile range [IQR]: 533-785) days, 28 (29.8%) adverse events occurred. Patients in the highest tertile of sST2 levels had increased risk of short-term (< 6 months) (adjusted hazard ratio [HR]: 8.36, 95% confidence interval [CI], 1.02-73.52; P < 0.05) and long-term adverse events (2 years) (adjusted HR: 4.23; 95% CI, 1.32-13.60; P < 0.01) than those in lower tertiles. The C-statistic was increased with addition of sST2 to BNP from 0.697 (95% CI, 0.541-0.852) to 0.812 (95% CI, 0.697-0.939) for short-term and from 0.712 (95% CI, 0.604-0.819) to 0.798 (95% CI, 0.697-0.899) for prediction of long-term adverse events. An intermediate-risk subgroup was identified, and 24% had adverse events. When serial measurements were taken in a nested case-control subgroup, sST2 levels were constantly high in patients with late adverse events (> 6 months) but gradually decreased in nonadverse-event controls compared with 3-month and 6-month baseline levels. Conclusions: In patients with PDCM, serum sST2 levels are associated with adverse events and have robust prognostic value. Serial measurements of sST2 could help in managing patients for monitoring outcomes of treatment.