Background: Two-dimensional speckle tracking echocardiography can be used to measure the effects of type 2 diabetes, which include increased epicardial adipose tissue and impaired right ventricular performance. This study aimed to evaluate the impact of type 2 diabetes mellitus (T2DM) on right ventricular function and its relationship with epicardial adipose tissue (EAT) thickness. Methods: This case-control study included 92 patients categorized into two groups: group I included 29 non-T2DM patients enrolled as a control group, group Ⅱ included 63 T2DM patients. All T2DM patients were divided into two groups according to their epicardial adipose tissue (EAT) thickness: group II-A included 33 T2DM patients with EAT thickness <5mm and group II-B included 30 T2DM patients with EAT thickness >5 mm. Right ventricular function and EAT thickness were measured using two-dimensional speckle tracking echocardiography (2DSTE). Results: Epicardial fat thickness was significantly lower in the control group than in both the EAT < 5 mm group and the EAT >5mm group. Also, the EAT < 5 mm group had a lower EAT thickness when compared to the EAT >5mm group. The RV LS and RV LSR-E and TAPSE were significantly higher in the control group than in the EAT >5mm group. Also, the RV LS and RV LSR-E and TAPSE were significantly higher in EAT <5mm when compared to the EAT >5mm group. Conclusion: This study highlighted the significant relationship between increased epicardial adipose tissue thickness and impaired right ventricular function in patients with type 2 diabetes mellitus.