BACKGROUND Transient atrial fibrillation (AF) following percutaneous patent foramen ovale (PFO) closure is common. Anticoagulation therapy should be considered in selected cases of prolonged AF after PFO closure, but guidelines do not provide clear recommendations on indication or choice of anticoagulant therapy for patients with post-procedural AF. CASE REPORT A 45-year-old woman presented with cryptogenic stroke verified by magnetic resonance imaging (MRI). Echocardiography revealed a PFO, which was closed percutaneously using a Gore septal occluder (25 mm). She was discharged on aspirin monotherapy (75 mg oral daily) according to institutional standard. Three weeks later, she presented with atrial fibrillation (AF). A direct oral anticoagulant (DOAC) (rivaroxaban 20 mg once daily) was initiated and aspirin was discontinued. After 4 months of follow-up, a routine echocardiography revealed large thrombi attached to both sides of the PFO occluder. CONCLUSIONS DOACs may be ineffective in preventing thrombus formation on device surfaces. Until more evidence has been provided, we suggest that DOACs are not routinely used for stroke prevention in patients following PFO closure or similar procedures within the first 3 months after device implantation.