BACKGROUND: The paper aimed to explore the significance of serum soluble ST2 (sST2) and circulating cell-free DNA (cfDNA) in predicting cardiac functions in children with severe pneumonia complicated by myocardial damage. METHODS: This case series study evaluated the serum sST2 and cfDNA levels of 60 children with severe pneumonia complicated by myocardial damage, assessing clinical data, biomarker levels, and cardiac function. RESULTS: We analyzed data from a cohort of 60 patients with a mean age of 4.47±1.88 years and a male: female ratio of 28:32. At baseline, patients had elevated levels of serum biomarkers, including sST2 and cfDNA, which were associated with cardiac function parameters and clinical outcomes. After 6 months, patients showed significant correlations between sST2, cfDNA, and cardiac function parameters, including left ventricular end-diastolic diameter (LVEDd), left ventricular end-systolic diameter (LVESd), and E/A ratio. Multivariate analysis revealed that higher levels of sST2 and cfDNA were associated with increased LVEDd, LVESd, and E/A ratio, as well as a lower likelihood of improvement and a higher likelihood of 6-month readmission. CONCLUSIONS: These findings suggest that sST2 and cfDNA may be useful biomarkers for predicting cardiac function and outcomes in this patient population.