Background: Circulating soluble urokinase-type plasminogen activator receptor (suPAR), which can reflect immune activation and low-grade inflammation, may be a novel biomarker of cardiovascular disease. Methods: We investigated the potential association between suPAR and the prevalence of atrial fibrillation (AF) by analyzing patients with either sinus rhythm, paroxysmal atrial fibrillation (PAF), or non-paroxysmal atrial fibrillation (NPAF), which indicates either permanent or persistent AF. Results: Among 426 patients enrolled (mean age 71.4±9.2 years; 110 (25.8%) female), 310, 62, and 54 were diagnosed with sinus rhythm, PAF, and NPAF, respectively. NPAF was >10-fold more prevalent in the highest suPAR quartile (>3534 pg/mL; 32 (30.2%) of 106 patients) than in the lowest suPAR quartile (