Introduction: Atrial fibrillation and flutter (AF/AFL) are the most common arrhythmias encountered in the emergency department (ED); however, little information exists regarding the preventive management of patients with AF/AFL by emergency physicians (EPs). This study explored whether patients with AF/AFL received the recommended thrombo-embolic (TE) prophylaxis at discharge from the ED; patients’ TE risks, bleeding risks, and TE prophylaxis upon discharge from the ED were examined following assessment for symptomatic acute AF/AFL. Methods: Patients ≥18 years of age identified by the EP as having a diagnosis of acute AF/AFL confirmed by ECG were prospectively enrolled from three urban Canadian EDs. Using standardized patient enrollment forms, trained research assistants collected data on the patient’s demographics, TE risk (using the CHADS2 and CHA2DS2-VASc score), bleeding risk (using the HAS-BLED score), and management both in the ED and at discharge. Treating physicians were surveyed on their use of risk scores when making TE prophylaxis decisions as well as their estimate of the patient’s stroke and bleeding risk. Descriptive analyses were performed. Results: From a total of 196 patients, 62% were male and the mean age was 63 years (standard deviation [SD] ±14). Most patients had previous history of AF/AFL (71%); hypertension was documented in 40% of them and ≤10% had other risk factors (e.g., congestive heart failure, vascular disease, diabetes, previous stroke, transient ischemic attack). Based on the CHADS2 score and previous management, there was opportunity for new or revised antiplatelet/anticoagulant treatment by EPs in 19% of the patients. Consultations were requested in 28% of the patients, and the majority (89%) were discharged with anticoagulant or antiplatelet agents. EPs expressed concerns that an increased risk of falls, lack of access to facilities for INR monitoring, and significant cognitive impairment would affect their willingness to prescribe anticoagulation. Conclusion: Most patients in the ED with acute AF/AFL are receiving the recommended TE prophylaxis; however, given the significant morbidity and mortality associated with AF/AFL, improved short-term prescribing practices for anticoagulants would benefit 1 in 5 ED patients. More research on barriers to EPs prescribing anticoagulants is required to improve clinician comfort in treating this high-risk population.