Objective <p>This study aims to evaluate the association between NETs levels and SMPP severity.</p> Methods <p>From January 2023 to August 2024, we selected children hospitalized with mycoplasma pneumonia (MPP). They were divided into two groups: a non-severe group (MPP group, <i>n</i> = 100) and a severe group (SMPP group, <i>n</i> = 50). ELISA was used to detect the concentration of NETs in the serum of both groups. Bronchoalveolar lavage fluid (BALF) was collected from the affected and unaffected lungs of children in the SMPP group, and ELISA was used to measure the concentration of NETs in BALF.</p> Results <p>There was a statistically significant difference in the concentration of NETs in the serum between the MPP and SMPP groups (<i>P</i> &lt; 0.01). The concentration of NETs in the BALF of the affected lung in the SMPP group was higher than that in the intact lung (<i>P</i> &lt; 0.001). The concentration of NETs in the serum of the SMPP group was higher than that in BALF (<i>P</i> &lt; 0.001). The area under the receiver operating characteristic curve (ROC ) for serum NETs predicting SMPP was 0.820 (95% CI 0.760–0.884, <i>P</i> &lt; 0.001), with a sensitivity of 0.821 and specificity of 0.845, and a cutoff value of 18.50 ng/mL. The ROC AUC for predicting SMPP using serum NETs combined with C-reactive protein (CRP) and lactate dehydrogenase (LDH) was 0.894 (95% CI 0.845–0.942, <i>P</i> &lt; 0.001), with a sensitivity of 0.883 and specificity of 0.820.</p> Conclusion <p>Overactivated NETs in children with MPP may be related to the occurrence of SMPP.</p>