Obesity, a major health issue worldwide, is associated with increased cardiovascular risk, endothelial dysfunction, and arterial stiffness. Tadalafil has been demonstrated to improve vascular parameters. To evaluate the effect of a single 20 mg dose of tadalafil on flow-mediated dilation and hemodynamic and arterial stiffness markers. A randomized, double-blind, placebo-controlled study was conducted on 80 participants (41 assigned to placebo and 39 to tadalafil) with grade 1 obesity, to evaluate the acute effect of a single dose of 20 mg of tadalafil on flow-mediated dilation and hemodynamic and arterial stiffness markers. Tadalafil did not modify flow-mediated dilation. However, it significantly lowered systolic blood pressure (SBP) (130.6±17.1 vs. 125.0±12.7 mmHg, p=0.011), diastolic blood pressure (82.7±18.2 vs. 76.5±11.8 mmHg, p≤0.001), central systolic blood pressure (116.33±19.16 vs. 109.90±15.05 mmHg, p=0.001), the augmentation index (69.1±17.1 vs. 65.7±14.4, p=0.012), and brachial-ankle pulse wave velocity (1229.7±218.4 vs. 1164.0±181.7, p=0.001). A single dose of tadalafil did not modify flow-mediated dilation in patients with grade 1 obesity but improved blood pressure and brachial-ankle pulse wave velocity.