In the era of drug-eluting stents (DES), a long-term dual antiplatelet therapy is required to prevent late stent thrombosis. However, in patients with atrial fibrillation (AF), there is a concern that combining warfarin with dual antiplatelet therapy may increase the risk of bleeding. We analyzed 1274 consecutive patients with coronary artery disease who were treated with coronary intervention from January 2006 through January 2009. Of these, we enrolled 74 AF patients treated with DES and dual antiplatelet therapy as well as warfarin. The primary endpoint was the incidence of major bleeding within 3 years; the predictive factor of major bleeding was also analyzed. To evaluate the efficacy of anticoagulant therapy, time in therapeutic range (TTR) was also measured. The 3-year incidence of major bleeding was 12.2 % (nine of 74 patients). The average observation period was 25.7 ± 20.2 months. Mean TTR value was 44.6 ± 33.0 % and was maintained at a relatively low level. Multivariate analysis revealed that a higher CHADS2 score (2-point more) was an independent predictor of increased risk of major bleeding. Major bleeding in the patients with triple antithrombotic therapy including warfarin occurred at a relatively high rate. Although the higher CHADS2-score indicates a high risk of thrombotic events, it was strongly associated with bleeding complications.