Background <p>Intravenous immunoglobulin (IVIG) resistance in Kawasaki disease (KD) is associated with coronary artery lesions (CALs). Available studies suggest that inflammation and nutritional status play a key role in IVIG resistance. Given this, the neutrophil percentage to albumin ratio (NPAR), a new combined indicator of inflammation and nutritional status, may be an important predictor of IVIG resistance.</p> Methods <p>This was a retrospective cohort study involving 591 children diagnosed with KD. Participants were categorized based on their NPAR levels, and their clinical data were analyzed to assess the relationship between NPAR and IVIG resistance. Multivariable logistic regression model was conducted to evaluate the association between inflammatory biomarkers and IVIG resistance. A restricted cubic spline (RCS) model was employed to investigate the dose-response relationship between NPAR, other inflammatory biomarkers, and the risk of IVIG resistance. Furthermore, subgroup analyses were performed to assess the effects of age, sex, and other relevant factors on the association between NPAR and IVIG resistance. The receiver operating characteristic curve (ROC) was utilized to estimate the predictive power of NPAR and other inflammatory biomarkers.</p> Results <p>Among 591 participants with KD, 72 (12.2%) were IVIG resistance, and these patients showed a higher incidence of CALs (26.4% vs. 11.6%). Higher NPAR levels were significantly associated with an increased proportion of IVIG resistance. Specifically, the proportion of IVIG resistance was 2.5% in the lowest NPAR tertile, compared to 25.4% in the highest tertile (<i>p</i> &lt; 0.001). The multivariable logistic regression model confirmed that NPAR was significantly associated with IVIG resistance. Each unit increase in NPAR was linked to 14.53 times increase in the odds of IVIG resistance (OR: 15.53, 95% CI: 7.83–30.84, <i>p</i> &lt; 0.001). After adjusting for confounders such as age, gender, and laboratory parameters, the association remained strong (OR: 21.80, 95% CI: 8.84–53.74, <i>p</i> &lt; 0.001). Additionally, the study demonstrated a dose-response relationship between NPAR levels and IVIG resistance, with higher NPAR values corresponding to greater risk. Subgroup analyses confirmed the stability of these findings. Furthermore, the area under the curve (AUC) for NPAR predicting IVIG resistance was 0.794, outperforming other inflammatory biomarkers.</p> Conclusion <p>This study demonstrated that NPAR, as a comprehensive indicator of inflammation and nutritional status, was significantly associated with IVIG resistance and can serve as a reliable predictor. Although the clinical application value of NPAR requires further validation, it shows promise as a novel biomarker for early identification of high-risk individuals and improving clinical management strategies.</p> Clinical trail number <p>Not applicable.</p>