Purpose <p>To investigate the clinical indicators that can predict myocardial damage in children with mycoplasma pneumoniae pneumonia (MPP) to help early identification and management.</p> Methods <p>The clinical data of 123 MPP children admitted from December 2023 to February 2024 in the affiliated Changzhou Children’s Hospital of Nantong University were analyzed retrospectively. According to the creatine kinase isoenzyme (CK-MB) level, the children were divided into 61 cases without myocardial damage group and 62 cases with myocardial damage group. Clinical manifestations and laboratory parameters were compared between the two groups. The factors affecting myocardial damage in children with MPP were analyzed by logistic regression. The ROC curve analyzed the predictive value of relevant indicators for myocardial damage in children with MPP.</p> Results <p>The incidence of abnormal electrocardiogram (ECG), extrapulmonary manifestations (except myocardial damage), white blood cell count (WBC), neutrophil/lymphocyte ratio (NLR), erythrocyte sedimentation rate (ESR), albumin and other myocardial enzyme parameters in the myocardial damage group were higher than those in the group without myocardial damage (<i>P</i> &lt; 0.05), and the median age and platelet/neutrophil ratio (PNR) were lower than those in the group without myocardial damage (<i>P</i> &lt; 0.05); there was no significant difference in general data such as gender, duration of fever, length of hospital stay, the incidence of severe pneumonia between the two groups (<i>P</i> &gt; 0.05); multivariate logistic regression analysis showed that median age, NLR level and extrapulmonary manifestations (except myocardial damage) were the main factors affecting myocardial damage in children with MPP (<i>P</i> &lt; 0.05); considering the interaction between NLR and PNR. We also performed ROC curve analysis for PNR. Among the univariate factors, PNR had the highest predictive value, and the specificity was as high as 86.9%. The combined area under the curve of the four indicators was 0.747, higher than that of the univariate factor (<i>P</i> &lt; 0.001), with a predictive sensitivity of 83.9% and a specificity of 63.9%.</p> Conclusion <p>Children with MPP younger than 6.79 years have extrapulmonary manifestations (acute sinusitis, acute otitis media, etc.), NLR &gt; 2.41, and PNR &lt; 44.74 in blood routine are more likely to develop myocardial damage.</p> Clinical trial number <p>Not applicable.</p>