Background New-onset postoperative atrial fibrillation (POAF) complicates 30% of cardiac surgeries. Although POAF is often transient, structured follow-up care of patients with POAF may identify those with paroxysmal or persistent atrial fibrillation (AF) who will benefit from evidence-based therapies. Methods This retrospective study includes patients seen in a clinic dedicated to patients with POAF after cardiac surgery between 2020 and 2024. Per the clinic’s operating procedure, patients wore a 14-day continuous ambulatory electrocardiogram (ECG) monitor fpr 2 months after surgery and were assessed thereafter in clinic. The primary outcome was recurrent AF lasting ≥ 30 seconds, captured by 14-day continuous ambulatory ECG or during clinical care. Results The cohort included 881 patients, with a mean age of 68 ± 9 years, and a median Congestive Heart Failure, Hypertension, Age ≥ 75 Years, Diabetes Mellitus, Stroke, Vascular Disease, Age 65 to 74 Years, Sex Category (CHA2DS2-VASc) score of 2 (interquartile range [IQR] 1-3); 529 patients (60.0%) underwent isolated coronary artery bypass grafting. At discharge, 798 patients (90.6%) were prescribed amiodarone, and 435 (49.4%) were prescribed oral anticoagulation. The mean time between discharge and 14-day continuous ambulatory ECG monitor was 72 days (IQR 61-84). AF recurrence was detected in 94 patients (10.7%); 30 patients (36.1%) were not receiving oral anticoagulation at the time of recurrence. Among patients with recurrence detected by 14-day continuous ambulatory ECG, the median duration was 10 hours (IQR 2-253). Left atrial volume index was the only independent predictor of AF recurrence. Following the clinic visit, oral anticoagulation was continued in 122 patients (28.2%). Conclusions Among patients with POAF following cardiac surgery, 1 in 10 have AF recurrence, as determined by a structured 14-day continuous ambulatory ECG monitor utilized 2-3 months postoperatively.