Background and Aims Metal stents and intraluminal irradiation with ¹²⁵I seeds are the preferred non-surgical treatments for malignant biliary obstruction, with proven efficacy in improving patient survival outcomes. However, the incidence of restenosis in metal stents remains high, and the factors contributing to this are not well understood, with no reliable predictive models currently available. Therefore, this study investigated the factors influencing metal stent restenosis in malignant biliary obstruction, developed a predictive model, and validated its performance.Methods A total of 110 patients with malignant biliary obstruction who received metal stents and ¹²⁵I seed intraluminal irradiation for the first time between January 2019 and March 2022 were selected. Patients were divided into restenosis and non-restenosis groups based on whether restenosis occurred within 12 months after operation. Univariate analysis and LASSO regression were initially used to screen for characteristic variables associated with stent restenosis, followed by Logistic regression to further analyze the related influencing factors. A nomogram predictive model was constructed using R language, and its value was assessed using the concordance index (C-index), Hosmer-Lemeshow goodness-of-fit test, the area under the receiver operating characteristic curve (AUC), and clinical impact curves. An additional 50 patients with malignant biliary obstruction from the same center, who received metal stents and ¹²⁵I seed intraluminal irradiation for the first time during a different period, were selected as an external validation dataset, and the κ statistic was used to compare the concordance rate between the nomogram prediction of restenosis and clinical reality.Results Of the 110 patients, 58 cases of restenosis occurred within 12 months after operation. Univariate analysis showed that diabetes, total bilirubin (TBIL), carbohydrate antigen 19-9 (CA19-9), postoperative biliary infection, gallstones, albumin level, radiofrequency ablation, and photodynamic therapy were associated with restenosis (all P<0.05). Logistic regression analysis identified TBIL, CA19-9, postoperative biliary infection, gallstones, radiofrequency ablation, and photodynamic therapy as independent factors associated with metal stent restenosis in malignant biliary obstruction (all P<0.05). The nomogram predictive model based on Logistic regression had a C-index of 0.838, and the Hosmer-Lemeshow goodness-of-fit test indicated no significant difference between the predicted and observed values (χ²=2.796, P=0.803). The AUC of the constructed nomogram for predicting metal stent restenosis in malignant biliary obstruction was 0.838 (95% CI=0.762-0.913), and the clinical impact curve showed a high concordance between the predicted high-risk group and actual outcomes across various threshold probabilities. Using the nomogram predictive model to predict the external validation dataset showed a concordance rate of 94.00% between the predicted restenosis rate and the actual one, with a κ value of 0.880.Conclusion TBIL, CA19-9, postoperative biliary infection, gallstones, radiofrequency ablation, and photodynamic therapy are independent factors associated with metal stent restenosis in malignant biliary obstruction. The predictive model based on these factors demonstrates good predictive ability and may provide a reference for early clinical identification of high-risk patients.