Stress urinary incontinence (SUI) may appear after the correction of pelvic organ prolapse (POP). The aim of this study was to externally validate a described predictive model for de novo SUI and to assess its clinical performance when used as a diagnostic test. This was a retrospective descriptive study on a cohort of consecutive women treated in our institution. The main outcome used to validate the model was the presence of objective or subjective SUI 1 year after surgery. A receiver operating characteristic curve was generated from our population to evaluate the predictive accuracy and to compare it with the original model. A cutoff point of ≥50% was used to evaluate its clinical performance as a diagnostic test. Of the full cohort, 169 women were suitable for analysis. The rate of de novo SUI was 11.8%. The predictive accuracy of the model in our population was similar to the original [area under the curve (AUC) = 0.69; 95% confidence interval (CI) = 0.58-0.80). However, its performance measures when evaluated as a diagnostic test were low: positive likelihood ratio = 2.71 and negative likelihood ratio = 0.86. Only 15 women presented a positive test result. External validation of the model found a global predictive accuracy similar to that of the original model. Despite the study being underpowered to give firm conclusions, the test did not show a good clinical performance when applied to our population with low de novo SUI prevalence. A larger sample size is needed to validate the model conclusively.