Background Data on Device-related Thrombus (DRT) after left atrial appendage closure (LAAC) remain scarce. This study aimed to investigate risk factors for DRT from centers reporting to the EUROC-DRT registry. Methods We included 537 patients (112 with DRT and 425 without DRT) who had undergone LAAC between 12/2008 and 04/2019. Baseline and implantation characteristics, anti-thrombotic treatment and clinical outcomes were compared between both groups in uni- and multivariate analyses. Additional propensity-score matching (PSM) was conducted to focus on the role of implantation characteristics. Results Patients with DRT showed higher rates of previous stroke/transient ischemic attack (TIA) (49.1% vs. 34.7%, p < 0.01), spontaneous echocardiographic contrast (SEC) (44.9% vs. 27.7%, p < 0.01) and lower left atrial appendage (LAA) peak emptying velocity (35.4 +/- 18.5 vs. 42.4 +/- 18.0 cm/s, p= 0.02). Occluders implanted in DRT patients were larger (25.5 +/- 3.8 vs. 24.6 +/- 3.5 mm, p =0.03) and implanted deeper in the LAA (mean depth: 7.6 +/- 4.7 vs. 5.7 +/- 4.7 mm, p