BACKGROUND High levels of TP53 protein can lead to apoptosis of myocardial cells. However, TP53 protein influence of myocardial damage remains unclear. This prospective study investigated the involvement of TP53 protein in secondary myocardial damage in children up to 18 years of age. MATERIAL AND METHODS Serum TP53 protein, N-terminal prohormone B-type natriuretic peptide (NT-ProBNP), cardiac troponin-I (cTnI), and creatine kinase isoenzyme MB (CK-MB) concentrations were measured in 50 hospitalized patients with secondary myocardial damage, 50 hospitalized patients without myocardial damage, and 50 healthy individuals (control). Cardiac damage was diagnosed based on cTnI, NT-ProBNP, and CK-MB levels, with electrocardiographic evidence as the reference. The appropriate cut-off value of TP53 protein for secondary myocardial damage was analyzed by receiver operating characteristic (ROC) curves. RESULTS The serum TP53 protein, NT-ProBNP, cTnI, and CK-MB concentrations of the patients with and without myocardial damage were 10.20±1.20 and 0.30±0.10 ng/L, 505.30 and 107.8 ng/L, 0.23±0.13 and 0.02±0.01 μg/L, and 28.30±5.13 and 12.24±4.29 IU/L, respectively. For the 50 patients with myocardial damage, the area under the ROC curve for serum TP53 protein, NT-ProBNP, cTnI, and CK-MB concentrations were 0.89 (95% CI: 0.81-0.95), 0.83 (95% CI: 0.77-0.91), 0.92 (95% CI: 0.84-0.97), and 0.85 (95% CI: 0.78-0.93), respectively, and the diagnostic cut-off values were 12.00 ng/L, 500.00 ng/L, 0.16 μg/L, and 27.00 IU/L, respectively, with positive likelihood ratios of 20.8, 13.2, 24.6, and 15.6. CONCLUSIONS TP53 protein is a valid biomarker of secondary myocardial damage in pediatric patients and can be diagnostic.