Antithrombotic therapy is central to the management of atrial fibrillation. This analysis from the RHYTHM-atrial fibrillation (RHYTHM-AF) registry explored the appropriateness of antithrombotic therapy in relation to stroke risk and atrial fibrillation duration in patients with atrial fibrillation. RHYTHM-AF, a prospective multinational registry, enrolled consecutive adult patients with atrial fibrillation considered for cardioversion. We compared the type of antithrombotic therapy administered at the time of cardioversion and at discharge with stroke risk ("high stroke risk" defined by CHA(2)DS(2)-VASc >1) and duration of atrial fibrillation (48 hours or unknown duration). Of 2,972 patients who were cardioverted (34.5% through pharmacologic cardioversion [PCV] and 65.5% through electrical cardioversion [ECV]), 65% were at high risk of stroke and 30% presented with atrial fibrillation of >48-hour or unknown duration. At the time of PCV and ECV, 36% (n = 242) and 84% (n = 1,075) of high-risk patients, respectively; were taking vitamin K antagonists or heparin. At discharge, these rates increased to 62% (n = 414) and 93% (n = 1,191), respectively. Of all low stroke risk patients with short-duration atrial fibrillation undergoing PCV (n = 260) and ECV (n = 111), 7% (n = 17) and 30% (n = 33), respectively, were taking vitamin K antagonists or heparin at the time of cardioversion. At discharge, these rates increased to 19% (n = 50) and 40% (n = 44), respectively. In conclusion, ECV was frequently performed under appropriate antithrombotic therapy for most high-risk patients with atrial fibrillation, whereas PCV was frequently performed without appropriate antithrombotic therapy. To enhance pericardioversion stroke prevention, cardioversion algorithms should focus less on the type of conversion and more on stroke risk factors and atrial fibrillation duration.