Objective: Cardiovascular involvement due to iron overload is the leading cause of morbidity and mortality in patients with beta-thalassaemia major (β-TM). However many patients remain asymptomatic until the late stage. In this study, we investigated the role of real-time three-dimensional echocardiography (RT3DE) findings and endothelial dysfunction parameters in asymptomatic β-TM patients, and the relationship between these parameters and cardiac magnetic resonance imaging (MRI) T2 * value. Methods: 51 asymptomatic β-TM patients who were receiving regular blood transfusions were evaluated by two-dimensional echocardiography (2DE) and RT3DE examinations including endothelial dysfunction parameters. The study population was divided into two subgroups based on their cardiac MRI T2* values (MRI T2* ≤20ms and >20ms). The relationships between serum ferritin levels, 2DE and RT3DE measurements, endothelial dysfunction parameters, and cardiac MRI T2* values were investigated. Results: Although all left ventricle ejection fraction (LVEF) values obtained by 2DE were within normal limits (≥50%), they were not associated with MRI T2* values. LVEFRT3D (53.25 +2.33 vs 58.81 +1.02), SDI12 (6.53 +0.56 vs 2.85 +0.48), SDI16 (7.65 +0.75 vs 3.26 +0.49) were significantly different and negatively correlated between two groups respectively . Flow-mediated dilatation (FMD) (6.08% + 0.34 vs 14.46% + 1.12), aortic strain (7.79% + 2.19 vs 12.76% + 4.19), and serum ferritin values were significantly different and negatively correlated between two groups respectively. Conclusion: Decreased LVEF and increased SDI by RT3DE could be parameters of early cardiac deterioration. Decreased FMD and aortic strain may be good predictors of subclinical cardiovascular involvement in asymptomatic patients with β-TM.