Abstract Background/Introduction Epicardial adipose tissue (EAT) accumulation is associated with adverse prognosis in patients with HFpEF and a better prognosis in HFrEF patients. Whether EAT is playing a protective role in dilated cardiomyopathy (DCM) patients have been described sparingly. Purpose Aim to explore whether the epicardial fat would change along with the dynamic changes in cardiac function and volumes after receiving guideline-directed medical therapy (GDMT) in patients with DCM. Methods We prospectively enrolled 232 DCM patients who underwent complete baseline and follow-up Cardiac magnetic resonance (CMR) examinations. The measurement of the epicardial fat composition includes epicardial fat thickness, paracardial fat thickness, and paracardial fat volume, while the measurement of body fat composition includes subcutaneous and visceral abdominal fat, while We used univariable and multivariable logistic regression to evaluate the association between different body and cardiac fat depots with the changes in bi-ventricular structure (delta indexed EDV) and function (delta EF). Results The study included 232 patients (mean age 46.1±14.1 years, 157 (67.7%) males). After GDMT, we found that the visceral fat thickness and EAT (thickness and volume) tend to significantly increase. The increase in the (left ventricular reverse remodeling) LVRR group was significantly higher compared with the non-LVRR group. Independently with the changes of BMI and body fat depots, the increment of EAT was associated with the improvement in bi-ventricular function and volumes (significantly positively correlated with the improvement of LVEF (r = 0.499, p < 0.001), and RVEF (r = 0.482, p < 0.001), negatively correlated with delta LVEDVi (r = -0.407, p < 0.001), delta RVEDVi (r = -0.305, p < 0.001)). Conclusions After GDMT, the increment of EAT was positively correlated with the improvement of bi-ventricular structure and function, independent of the changes in BMI and body fat depots.Graphic Abstract