Background and Aim: Postmenopausal women are particularly vulnerable to hypertension and cardiovascular diseases due to hormonal changes following the cessation of estrogen production. These changes often lead to increased visceral fat, decreased muscle mass, and endothelial dysfunction, contributing to vascular problems. This study aimed to assess the impact of an eight-week aquatic exercise program on endothelin-1 (ET-1) levels and blood pressure in postmenopausal women with hypertension. ET-1 is a potent vasoconstrictor peptide that regulates blood vessel tone, and elevated levels of ET-1 are linked to the development of hypertension. Methods: This quasi-experimental study involved 22 postmenopausal women aged 50-65, diagnosed with hypertension. Participants were randomly assigned to an experimental group (n=11) that engaged in an eight-week aquatic exercise program and a control group (n=11). The exercise protocol included three 60-minute sessions per week, focusing on low-impact water walking, jogging, and resistance exercises. Blood samples for ET-1 measurement were taken before and after the intervention, and blood pressure was assessed at both time points. Results: The experimental group showed a significant reduction in ET-1 levels (P = 0.001) and blood pressure (systolic P = 0.002, diastolic P = 0.003) compared to the control group. The control group did not exhibit significant changes in ET-1 levels or blood pressure. Conclusion: This study suggests that an eight-week aquatic exercise program can significantly reduce ET-1 levels and improve blood pressure regulation in postmenopausal women with hypertension, offering a safe and effective non-pharmacological alternative for managing cardiovascular health in this population.