Atrial fibrillation may causes major problems during the perioperative period and its management requires a cooperation among the cardiologist, the surgeon, and the anesthetist. This is the most common arrhythmia in the population, especially among the elderly, and is generally treated with anticoagulants to avoid the risk of the formation of atrial thrombi and the consequent peripheral embolism. In patients affected by atrial fibrillation and undergoing surgery, the continuation of anticoagulation is associated with the risks of increased surgical bleeding, whereas the suspension of anticoagulants favors the formation of atrial thrombi. Hence, management should balance the two risks. Often, atrial fibrillation occurs during surgery or in the post-operative period, favored by sympathetic hyperactivity. In this case, the arrhythmia can cause not only an increase of the thromboembolic risk, but also a cardiovascular dysfunction due to the loss of the atrial pump or to the high ventricular rate. Restoration of sinus rhythm by electrical or pharmacological therapy and simple control of ventricular rate are both effective therapeutic strategies, the choice between them should be based on patient characteristics and on the clinical picture.