This study aimed to detect endothelial dysfunction in erectile dysfunction (ED) patients free from cardiovascular diseases or atherosclerotic risk factors and to evaluate acute effects of phosphodiesterase-5 inhibitor tadalafil on endothelial dysfunction and cardiac function. Thirty ED patients and 20 healthy male subjects (mean ages: 48.7 ± 11.7 and 48.3 ± 8.7 years, respectively) were enrolled. Endothelium functions were assessed by applanation tonometry. Aortic stiffness and cardiac function were evaluated by transthoracic echocardiography. Pulse pressure was greater in the ED group (P < 0.05), whereas aortic strain and aortic distensibility were significantly lower (P < 0.001). Treatment with tadalafil reduced pulse pressure (P = 0.0179), systolic blood pressure (P = 0.001) and diastolic blood pressure (P = 0.054) and increased aortic distensibility (P = 0.001) and aortic strain (P = 0.003) in the ED group. Tadalafil administration also increased large artery and small artery elasticity indices that were reduced in the ED group at baseline (P = 0.02 and 0.003, respectively). Systemic vascular disease and compromised left ventricular diastolic function (LVDF) were present in ED patients with no known atherosclerotic risk factors and cardiac diseases. Tadalafil positively affected arterial stiffness and LVDF.