Objective To investigate the correlation between serum levels of inflammatory mediators and pulmonary function in children with Mycoplasma pneumoniae pneumonia (MPP), and explore the predictive efficacy of inflammatory mediator levels in differentiating varying degrees of disease severity. Methods A cohort of 114 pediatric patients diagnosed with MPP and treated at our hospital from January 2023 to December 2024 was enrolled as the study population. Meanwhile, 100 pediatric patients with non-MPP infectious pneumonia during the same period were chosen as the control group (non-MPP group). Furthermore, the 114 MPP pediatric patients were further divided into a mild-case group (n=81) and a severe-case group (n=33) based on the severity of their illness. Spearman's partial correlation analysis was employed to examine the correlations. Multivariate logistic regression analysis was used to identify influencing factors. ROC curves were utilized to evaluate the predictive value. Results Compared with the non-MPP group, children in the MPP group exhibited lower serum levels of neutrophil- to-lymphocyte ratio (NLR), erythrocyte sedimentation rate (ESR), white blood cell count (WBC), procalcitonin (PCT), and interleukin-4 (IL-4), while higher levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). When comparing the severe-case MPP group with the mild - case MPP group, children in the severe-case group had higher serum levels of NLR, C-reactive protein (CRP), WBC, IL-4, and IL-6. Partial correlation analysis revealed that NLR, IL-6, and IL-4 were all negatively correlated with FVC. CRP was positively correlated with FVC. NLR was positively correlated with the ratio of FEV1/FVC, whereas IL-6 and IL-4 were negatively correlated with FEV1/FVC. However, no significant correlations were observed between the levels of PCT, TNF-α, ESR, WBC and pulmonary function indicators. The levels of CRP (OR=1.502), WBC (OR=3.224), IL-4 (OR=5.690), and IL-6 (OR=1.356) were identified as independent influencing factors for the severity of illness in pediatric patients with MPP. The ROC curve analysis demonstrated that the combined prediction model achieved the highest AUC of 0.990 (95% confidence interval: 0.978～1.000), with a sensitivity of 0.960 (95% confidence interval: 0.922～0.998) and a specificity of 0.962 (95% confidence interval: 0.911～1.000). Conclusion The levels of inflammatory mediators, namely CRP, WBC, IL - 4, and IL-6, exhibit good predictive value for the severity of illness in pediatric patients with MPP and show a certain degree of correlation with pulmonary function