Background: Impaired renal function and atrial fibrillation (AF) can form a vicious cycle. Although there have been reports on improved renal function in patients who undergo successful AF ablation, renal function in patients with recurrence of AF has not been studied separately. We explored the changes in renal function in AF patients with mild renal dysfunction after an index failed catheter ablation and the influencing factors. Methods: We retrospectively recruited non-valvular AF (NVAF) patients with mildly impaired renal function admitted for catheter ablation and readmitted due to recurrence of AF. The estimated glomerular filtration rate (eGFR) was calculated before the index procedure and during readmission. △eGFR was defined as the difference between eGFR readmission and eGFR baseline. The same calculation applied for △CHA2DS2-VASc score. The primary endpoint was improved renal function (△eGFR > 0) after AF catheter ablation in patients with atrial arrhythmia recurrence. Results: A total of 132 NVAF patients were included in this study. The mean eGFR at readmission was significantly increased compared with the eGFR at baseline before the index ablation procedure (P < 0.01). The multivariable Cox regression analysis showed that a lower △CHA2DS2-VASc score (HR: 0.416, P = 0.003) and paroxysmal recurrent atrial arrhythmia (HR: 2.965, P = 0.001) were associated with better renal function. Conclusion: In NVAF patients with mildly impaired renal function, even those with recurrence after the initial catheter ablation, we observed improvements in renal function, which was associated with a lower △CHA2DS2-VASc score and paroxysmal recurrent arrhythmia.