Background. Atrial fibrillation is one of the most common types of cardiac arrhythmias. The frequent combination of atrial fibrillation and coronary artery disease in clinical practice can be attributed to common risk factors and relationships among pathogenetic mechanisms.Aim. This study aims to evaluate the impact of atrial fibrillation on immediate and long-term clinical outcomes in patients undergoing percutaneous coronary intervention for coronary bifurcation lesions.Methods. This study included 709 patients who underwent percutaneous coronary intervention for coronary bifurcation lesions. All patients were divided into two groups: those with and without atrial fibrillation.Results. This multicentre registry showed that the incidence of atrial fibrillation was 11.7%. Compared to patients without a history of atrial fibrillation, those that did were older (66.8 ± 8.5 vs. 62.9 ± 9.0 years, p = 0.0002) and more often had cerebrovascular (22.9% vs. 10.4%, p = 0.003) and peripheral artery disease (18.1% vs. 7.2%, p = 0.002). The overall incidence of major adverse cardiovascular events at the hospital stage was 1.8%. The average follow-up duration was 476 ± 94 days. No difference in long-term major adverse cardiovascular events (15.0% vs. 13.1%, p = 0.6) was observed between patients with and without atrial fibrillation. Patients with atrial fibrillation were more likely to have adverse events, such as bleeding (13.8% vs. 9.3%, p = 0.22), stroke (2.5% vs. 1.0%, p = 0.23) and myocardial infarction (7.6% vs. 5.0%, p = 0.28), although differences between the groups were insignificant.Conclusion. Atrial fibrillation was not associated with mortality and major adverse cardiovascular events in patients undergoing percutaneous coronary intervention for coronary bifurcation lesions. ClinicalTrials.gov Identifier: NCT03450577 Received 4 August 2021. Revised 27 September 2021. Accepted 28 September 2021. Funding: The study did not have sponsorship. Conflict of interest: Authors declare no conflict of interest. Contribution of the authorsConception and study design: D.A. Khelimskii, O.V. Krestyaninov, A.G. Badoian, A.A. Baranov, R.B. Utegenov, I.S. Bessonov, S.S. SapozhnikovData collection and analysis: D.A. Khelimskii, A.G. Badoian, A.A. Baranov, R.B. Utegenov, I.S. Bessonov, S.S. SapozhnikovStatistical analysis: D.A. Khelimskii, A.G. Badoian, I.S. BessonovDrafting the article: D.A. Khelimskii, O.V. Krestyaninov, A.G. Badoian, A.A. Baranov, R.B. Utegenov, I.S. Bessonov, S.S. SapozhnikovCritical revision of the article: D.A. Khelimskii, O.V. Krestyaninov, A.G. Badoian, A.A. Baranov, R.B. Utegenov, I.S. Bessonov, S.S. SapozhnikovFinal approval of the version to be published: D.A. Khelimskii, O.V. Krestyaninov, A.G. Badoian, A.A. Baranov, R.B. Utegenov, I.S. Bessonov, S.S. Sapozhnikov