Objective <p>The present study aimed to analyze the risk factors affecting the prognosis children with fulminant myocarditis.</p> Methods <p>The medical records of all patients (<i>n</i> = 40) who were diagnosed with fulminant myocarditis and admitted to the Cardiac Intensive Care Unit (CICU) and Pediatric Intensive Care Unit (PICU) at the Guanzhou Women and Children's Medical Center, Guangzhou Medical University between January 2014 and December 2023 were retrospectively analyzed. Patients were divided into two groups based on their in-hospital prognosis, namely, a survival group (<i>n</i> = 32) and an non-survival group (<i>n</i> = 8). Baseline demographics, laboratory findings, electrocardiograms, echocardiograms, and treatment regimens were compared between the two groups via multifactorial analysis.</p> Results <p>The median age of patients in the survival group was 7.8&#xa0;years (M[5,11.5]), and the median age in the non-survival group was 9.0&#xa0;years (M[6,11.5]). Compared with those in the survival group, patients in the non survival group had significantly higher levels of extracorporeal cardiopulmonary resuscitation (ECPR) use, ventricular tachycardia/ventricular fibrillation (VT/VF), peak creatine kinase isoenzyme (CK-MB), peak N-terminal B-type natriuretic peptide precursor (NT-proBNP), serum creatinine (Scr) on admission, peak serum Scr, peak aspartate aminotransferase (AST), peak alanine aminotransferase (ALT), peak cardiac troponin I (cTnI), lactate on admission, peak lactate, and extracorporeal membrane oxygenation (ECMO) use (all <i>p</i> &lt; 0.05). Binary logistic regression analysis revealed that the peak lactate level was an independent risk factor for mortality in patients with fulminant myocarditis (OR = 0.661, 95% CI 0.488–0.897; <i>p</i> = 0.008).</p> Conclusions <p>The present study demonstrated that the peak lactate level is an independent risk factor for mortality in patients with fulminant myocarditis.</p>