Atrial fibrillation (AF) is the most common arrhythmia and often recurs despite catheter ablation. The recurrence of AF is often underdiagnosed by standard 24-hour electrocardiogram (ECG) because of its transient and silent nature. A garment-style ECG with a highly conductive textile electrode made of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)(PEDOTPSS) and nanofiber (Garment ECG) has been developed that can provide longer-term continuous monitoring. This study investigated whether 2-week Garment ECG can reveal instances of AF recurrence in patients who are diagnosed as remaining in sinus rhythm by 24-hour Holter ECG. The open-label randomized crossover study enrolled 67 patients (63.1±10.6 years old, 53 men) who had undergone initial AF ablation. Three months after ablation, patients were randomly assigned to group 1 (n = 35), 2-week Garment ECG followed by 24-hour Holter ECG, or group 2 (n = 32), 24-hour Holter ECG followed by 2-week Garment ECG. The detection of AF recurrence was compared between the two devices. The Garment ECG showed AF recurrence in 12 patients (18%) compared to 4 patients for the Holter ECG (6%, p = 0.008). The ECG acquisition rate was higher for Holter ECG than for Garment ECG (100.0% interquartile range 100.0-100.0% versus 82.4% 71.1-91.0%, p<0.001), but the Garment ECG provided longer total analysis time (11.0 days 9.0-12.2 days for Garment; 1.0 day 1.0-1.0 day for Holter, p<0.001). Despite the lower ECG acquisition rate, the 2-week Garment ECG revealed instances of AF recurrence after ablation in patients who were underdiagnosed by 24-hour Holter ECG. Clinical Trial Registration: URL: https://jrct.niph.go.jp/en-latest-detail/jRCTs032180018 Unique Identifier: jRCTs032180018.