Epicardial adipose tissue (EAT), as an endocrine organ, may serve as a source of pro-inflammatory cytokines. Also, given the strong relationship between atrial fibrillation (AF), obesity and inflammation, the purpose of this study was to investigate the association of non-valvular AF with epicardial and periatrial fat. A total of 618 (192 in sinus rhythm, 169 with paroxysmal AF, 133 with persistent AF and 124 with permanent AF) patients who underwent CT angiography for the evaluation of CAD or pulmonary vein anatomy before catheter ablation were enrolled in this study. Thickness of the EAT and periatrial fat were measured by CT angiography. Together with body mass index, these were examined in relation to the presence and severity of AF and left atrial (LA) diameter. Patients with AF had significantly more total EAT and periatrial fat thickness compared with patients in sinus rhythm (p < 0.001). EAT thickness was significantly higher in permanent, persistent and paroxysmal AF compared with sinus rhythm group (p < 0.001). Multivariable multinomial logistic regression analysis comparing patients with sinus rhythm and subtypes of AF revealed a significant association between periatrial fat and total EAT thickness with all AF subtypes. Correlation analysis demonstrated that both total EAT thickness and periatrial fat thickness were significantly correlated with LA diameter (p < 0.05). Epicardial fat thickness is associated with both the presence and severity of AF independent of all other risk factors including LA diameter. Mediators for the association of EAT with AF pathophysiology requires future large scale prospective studies.