Background: Serum uric acid (SUA) is a simple and independent marker of morbidity and mortality in a variety of cardiovascular diseases. In this study we aimed to investigate SUA and the risk of left atrial (LA) thrombus in patients with nonvalvular atrial fibrillation (AF). Methods: In this retrospective study, 1359 consecutive patients undergoing transesophageal echocardiography before catheter ablation of AF were enrolled. Sixty-one of the 1359 patients (4.5%) had LA thrombus. Results: SUA levels in patients with LA thrombus were significantly greater (413.5 +/- 98.8 mu mol/L vs 366.7 +/- 94.3 mu mol/L; P < 0.001). Hyperuricemia was defined as SUA >= 359.8 mu mol/L in women and >= 445.6 mu mol/L in men determined according to receiver operating characteristic curve. The incidence of LA thrombus was significantly greater in patients with hyperuricemia than in those with a normal SUA level in women (12.1% vs 1.9%; P < 0.001) and in men (8.5% vs 2.8%; P < 0.001). Hyperuricemia had a negative predictive value of 98.1% in women and 97.1% in men for identifying LA thrombus. Hyperuricemia was associated with significantly greater risk of LA thrombus among Congestive Heart Failure, Hypertension, Age >= 75 Years, Diabetes Mellitus, Stroke, Vascular Disease, Age 65 to 74 Years, Sex Category (CHA2DS2- VASc) score = 0, 1, and >= 2 groups with odds ratios of 7.19, 4.05, and 3.25, respectively. In multivariable analysis, SUA was an independent risk factor of LA thrombus (odds ratio, 1.004; 95% confidence interval, 1.000-1.008; P = 0.028). Conclusions: Hyperuricemia was a modest risk factor for LA thrombus, which might refine stratification of LA thrombus in patients with non-valvular AF.