Background Insulin resistance (IR) is an important disorder in obese children because it is closely related to cardiovascular diseases. Epicardial adipose tissue (EAT) plays a role in the development of IR due to secreted bioactive molecules, and the inflammatory process of these molecules may cause atrial electromechanical delay (EMD). Objective The objective of our study was to determine the relationship between EAT and EMD with IR in obese children. Methods Ninety-four obese patients were included in the study. IR was calculated using the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and defined as HOMA-IR greater than the 90thpercentile in an age- and sex-specific percentile curve. Patients were divided into two groups according to their IR. All patients underwent echocardiographic examinations. Statistical significance was set to a two-sided p-value < 0.05. Results EAT was significantly higher in the IR group (p < 0.001). The optimal cut-off value for EAT to predict IR was found to be > 3.85 mm, with 92.5% specificity and 68.5% sensitivity (p = 0.002). In the multivariate logistic regression model, EAT (OR = 1.256, 95% CI: 1.016-1.53, p = 0.035) was also associated with IR after adjustment for variables found to be statistically significant in univariate analysis. Inter- and intra-atrial EMD was significantly prolonged in the IR group compared to the group without IR (p < 0.010; p = 0.032 respectively). Conclusion: In our study, we revealed that EAT was positively correlated with IR and was an independent predictor of IR. (Arq Bras Cardiol. 2020; [online].ahead print, PP.0-0).