<i>Aim</i>.To validate the National Danish Ablation Database (NDAD) by investigating to what extent data in NDAD correspond to medical records. <i>Type of study</i>. Non-blinded, registry-based, retrospective, validation study. <i>Material and methods</i>. A sample of patients who underwent ablation for atrial fibrillation in Denmark between 1 January 2016 and 31 December 2016 were included. By utilizing medical records as gold standard, positive predictive (PPV) and negative predictive values (NPV) for NDAD were assessed and presented as five main categories: arrhythmia characteristics, demographics, cardiac history, complications, and medication. PPV’s and NPV’s exceeding 90% were considered as high agreement. <i>Results</i>. 597 patients (71.0% males) were included in the study. Median age was 63.1 (IQR: 54.9–68.4) years. The median PPV and NPV estimates across all variables were respectively 90.4% (95% CI: 68%–95.2%) (PPV) and 99.4% (95% CI: 98.4%–99.8%) (NPV) at baseline, and 91.7% (95% CI: 67.4%–95.4%) (PPV) and 99.3% (98.2%–99.3%) (NPV) at follow-up. <i>Conclusion</i>. The data registered in NDAD agrees to a great extent with the patients’ medical records, suggesting NDAD is a database with high validity. As a result of low complication rate, the PPV- and NPV-estimates among complication variables were prone to somewhat greater uncertainty compared to the rest.