Purpose <p>Perineural invasion (PNI) is an independent predictive factor for pancreatic ductal adenocarcinoma (PDAC); however, preoperative prediction is difficult. This study aimed to evaluate the value of dual-layer spectral CT (DLCT) parameters in PNI in PDAC.</p> Materials and methods <p>This retrospective study included patients with pathologically confirmed PDAC who underwent DLCT between August 2019 and March 2024. Risk factors were identified using univariable and least absolute shrinkage and selection operator (LASSO) regression. Receiver operating characteristic (ROC), precision-recall (PR) curves, calibration curves and decision curve analysis (DCA) accessed diagnostic performance.</p> Results <p>We included 100 patients (mean age: 60.88 ± 11.39 years old, 59 males). There were 71 patients with PNI and 29 without PNI. Relevant factors for PNI included tumour diameter, normalised CT attenuation during the pancreatic parenchymal phase in conventional CT (nCTa), normalised CT attenuation during the pancreatic parenchymal phase in DLCT at 40&#xa0;keV, and normalised iodine concentration during the pancreatic parenchymal phase (nDIa) (odds ratio [OR], 1.34; 95% confidence interval [CI]: 1.19, 1.51; <i>p</i> &lt; 0.001). Of these, nDIa was the only independent predictor (<i>p</i> &lt; 0.001; adjusted OR, 1.41; 95% CI: 1.19, 1.68) and demonstrated superior diagnostic performance compared to nCTa, with a cutoff value of 0.16, higher area under the curve (ROC: 0.86 vs. 0.68, PR: 0.93 vs. 0.84; both <i>p</i> &lt; 0.001), higher accuracy (77.0% vs. 52.0%, <i>p</i> = 0.048), an F₁ score of 0.90, higher sensitivity (71.8% vs. 36.6%, <i>p</i> = 0.03), and the same specificity of 89.7% (<i>p</i> = 0.13). The calibration plot illustrated satisfactory agreement of nDla and DCA confirmed its promising clinical application value.</p> Conclusion <p>The DLCT parameter nDIa allows for non-invasive prediction of PNI in PDAC with superior diagnostic efficacy compared to conventional CT parameters.</p>