BACKGROUND The utility of an ultra-high-resolution electroanatomical mapping system (UHR-EAM, Rhythmia) for repeat atrial fibrillation (AF) ablation has not been evaluated. OBJECTIVE A second AF ablation procedure performed using UHR-EAM may demonstrate different outcomes compared with that using a conventional electroanatomical mapping system (C-EAM, CARTO3). METHODS This observational study enrolled consecutive patients who underwent a second AF ablation procedure using UHR-EAM (n = 103) and C-EAM (n = 153). The second ablation procedure included re-isolation of reconnected pulmonary veins (PVs) and elimination of clinical or induced non-PV AF triggers and atrial tachycardia (AT). Other empirical ablations were additionally conducted at the discretion of the operators. RESULTS Re-isolation of PVs was achieved in 196 patients who had ≥1 left atrial-PV reconnection. The elimination rate of AT was higher in the UHR-EAM group than the C-EAM group (87% vs 65%, P = .040), while that of non-PV AF triggers was similar (63% vs 63%, P = 1.00). The UHR-EAM demonstrated shorter radiofrequency application time (21.8 ± 16.8 vs 28.0 ± 21.3 minutes, P = .017), but longer fluoroscopic time (26.2 ± 12.6 vs 21.4 ± 9.3 minutes, P = .0001). No severe complication developed. The total 1-year AF/AT-free survival rates were similar between the two groups (off AADs, 59.2% vs 56.2%, P = .62; on AADs, 65.0% vs 69.3%, P = .49). CONCLUSIONS The efficacy and safety outcomes of repeat AF ablation using UHR-EAM was comparable to those using C-EAM.