OBJECTIVES: Atrial fibrillation (AF) is common in patients with hypertrophic cardiomyopathy (HCM) and it is often poorly tolerated because of loss of atrial contraction and reduced filling time with rapid ventricular rates. Restoring sinus rhythm is of great clinical benefit to HCM patients. Very few data exist regarding surgical ablation of concomitant AF in this setting. The aim of this study was to evaluate the mid-term outcome of surgical AF ablation in patients who underwent cardiac surgery due to HCM. METHODS: Thirty-one consecutive patients with primary HCM and drug-refractory symptomatic AF underwent surgical ablation with concomitant septal myectomy (77%) and/or mitral valve repair/replacement (39%). Follow-up was 97% complete with a median of 6.4 years [3.8-9.1]. RESULTS: Hospital mortality was 6% and the overall survival at 7 years was 87 ± 6.1%. No stroke and thromboembolic events were documented at follow-up. The arrhythmia-free survival off antiarrhythmic drugs was 82 ± 7.3% at 1 year and 52 ± 10.2% at 6 years. The 1- and 6- year arrhythmia control (maintenance of sinus rhythm with or without antiarrhythmic drugs) was 96 ± 3.5 and 80 ± 8.1%, respectively. The recurrent arrhythmia was AF in all patients. No predictors of AF recurrence were detected. CO NCLUSIONS: Concomitant surgical ablation of AF is a reasonable treatment option for drug refractory AF in patients with HCM undergoing surgical myectomy and/or mitral valve surgery. However, chronic antiarrhythmic drugs are needed to achieve a satisfactory mid-term arrhythmia control. © The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.