Background: Atrial fibrillation is common in patients with mitral regurgitation (MR) and has a negative impact on the clinical outcome of patients with valvular heart disease. We aimed to evaluate the impact of pre-procedural atrial fibrillation on the long-term clinical outcomes of patients with MR undergoing transcatheter mitral valve repair by MitraClip implantation. Methods: We analysed 355 consecutive patients with and without atrial fibrillation with symptomatic, severe MR and inoperability or high surgical risk undergoing MitraClip implantation in a three-year follow-up. Results: In patients with pre-procedural atrial fibrillation undergoing MitraClip implantation, we found advanced age, higher baseline NT-pro-BNP levels, increased left atrial diameter, and higher rate of severe tricuspid regurgitation, compared to patients with sinus rhythm. In the three-year follow-up after MitraClip implantation, mortality and major adverse cardiovascular and cerebral events (MACCE) occur significantly more often in patients with atrial fibrillation, compared to patients without atrial fibrillation. Multivariate regression analysis confirmed atrial fibrillation (hazard ratio 2.39, 95%-confidence interval 1.06⁻5.41, p = 0.036) as an independent predictor for three-year-mortality after MitraClip implantation. Conclusions: Atrial fibrillation is an independent predictor for long-term mortality after MitraClip implantation. We demonstrate the association of atrial fibrillation with mortality and MACCE in the long-term follow-up of patients undergoing MitraClip implantation.