IntroductionThe optimal antithrombotic strategy for patients with atrial fibrillation (AF) undergoing percutaneous coronary intervention (PCI) is uncertain. For patients with non-AF, many trials are now evaluating short 1-month dual antiplatelet therapy. In patients with AF undergoing PCI, in contrast, short dual therapy (P2Y₁₂ inhibitor +direct oral anticoagulant (DOAC)) has not yet been evaluated.Methods and analysisThe OPTIMA-AF trial (OPTIMAl antiplatelet therapy in combination with direct oral anticoagulants in patients with non-valvular Atrial Fibrillation undergoing percutaneous coronary intervention with everolimus-eluting stent) is an investigator-initiated, open-label, nationwide, multicentre, prospective, randomised controlled trial. The primary objective is to compare the efficacy and safety of short dual therapy (1-month DOAC +P2Y₁₂ inhibitor followed by DOAC monotherapy) against long dual therapy (12-month DOAC +P2Y₁₂ inhibitor followed by DOAC monotherapy) in the treatment of AF subjects undergoing PCI. The primary efficacy endpoint is a composite of death or thromboembolic events (myocardial infarction, definite stent thrombosis, stroke or systemic embolism) at 365 days; and the primary safety endpoint is bleeding (International Society on Thrombosis and Haemostasis major or clinically relevant non-major bleeding) at 365 days. This trial is intended to show the non-inferiority of short dual therapy versus long dual therapy in terms of the primary efficacy endpoint and show superiority in terms of the primary safety endpoint. A total of 1090 subjects will be randomised in a 1:1 ratio at approximately 60 sites.Ethics and disseminationThis study received approval from the Certified Review Board of Osaka University (a certified research ethics committee by the Japanese Clinical Research Act). The findings will be disseminated through peer-reviewed publications and conference presentations.Trial registration numberJapan Registry of Clinical Trials: jRCTs051190053; Pre-results.