This study aimed to evaluate the relationship between serum transforming growth factor-β1 (TGF-β1) concentration and atrial fibrosis and to determine whether plasma TGF-β1 concentration is an independent predictor of atrial fibrillation (AF) recurrence after catheter ablation.We included 98 consecutive patients who underwent catheter ablation, including 38 with paroxysmal AF (AF group) and 60 with paroxysmal supraventricular tachycardia (control group). We compared their preablation serum concentration of biomarkers and clinical and echocardiographic findings.Serum TGF-β1 concentrations, type-III procollagen N-terminal peptides (PIIINP), type-IV procollagen (IV-C), and laminin (LN) were significantly higher in the AF group than in the control group; however, there was no correlation between their concentrations and left atrial diameter (LAD). The area of the low-voltage zone positively correlated with TGF-β1 and PIIINP concentrations, but not with LAD. Atrial tachyarrhythmia (AF and AFL/AT) recurrence was observed in 15 patients (39.4%) at mean 241.4 ± 68.5 days of follow-up 12 months after ablation. Regression analysis revealed that TGF-β1 was a major risk factor for AF recurrence (odds ratio, 1.14; 95% confidence interval, 1.11-1.17; P = .02).Serum TGF-β1 concentration is an independent predictor of AF recurrence in patients with paroxysmal AF and may help identify patients likely to have better outcomes after catheter ablation.