Background <p>There is mounting evidence suggesting a direct connection between inflammatory responses and the pathophysiology of overactive bladder (OAB). However, conventional inflammatory markers do not directly indicate a correlation with OAB. Therefore, our goal was to investigate the relationship between OAB and a novel inflammatory marker, the neutrophil percentage-to-plasma-albumin ratio (NPAR).</p> Methods <p>This study included 28,906 participants from the 2005–2018 National Health and Nutrition Examination Survey (NHANES). Weighted multivariate regression models and multiple regression equations were applied to evaluate the correlation between NPAR and OAB. Additionally, to evaluate the possibility of a linear relationship between NPAR and OAB, smoothed curve fitting was used. Sensitivity and stratified analyses were conducted to assess the robustness of the results.</p> Results <p>The final sample size consisted of 28,906 individuals, with an overall OAB prevalence of 24.6%. Using a weighted multivariate logistic model and adjusting for multiple covariates, we identified a strong association between NPAR and OAB (OR 1.074, 95% CI 1.06–1.08). Individuals in the highest NPAR quartile had a 32% greater prevalence of OAB compared to those in the lowest quartile. Smoothed curve fitting showed a nonlinear connection between NPAR and OAB, and the effect sizes remained consistent across specific subgroups (P for interaction &lt; 0.05).</p> Conclusion <p>The incidence of OAB was shown to positively correlate with higher NPAR levels in this investigation. NPAR might be a useful and affordable biomarker for determining who is at risk for OAB, facilitating timely intervention.</p>