Background: Up-regulation of the erythropoietin (EPO) /EPO-receptor (EPOR) system plays protective role against chronic hypoxia-induced pulmonary hypertension (hypoxic PH) through enhancement of endothelial nitric oxide (NO)-mediated signaling. Genistein (Gen), a phytoestrogen, is considered to ameliorate NO-mediated signaling. Objective: We hypothesized Gen attenuates and prevents hypoxic PH. Methods and Results: In vivo, Sprague-Dawley rats raised in a hypobaric chamber were treated with Gen (60mkg·kg^-1) for 21 days. Pulmonary hemodynamics and vascular remodeling were ameliorated in Gen-treated hypoxic PH rats. Gen also restored cGMP levels, phosphorylated endothelial NO synthase (eNOS) at Ser¹¹⁷⁷ and Akt at Ser⁴⁷³ expression in the lungs. Additionally, Gen potentiated plasma EPO concentration and EPOR-positive endothelial cell counts. In experiments with hypoxic PH rats' isolated perfused lungs, Gen caused NO- and phosphatidylinositol 3-kinase (PI3K)/Akt-dependent vasodilation that reversed abnormal vasoconstriction. In vitro, a combination of EPO and Gen increased the phosphorylation of eNOS and the EPOR expression in human umbilical vein endothelial cells under a hypoxic environment. Moreover, Gen potentiated the hypoxic increase in EPO production from human hepatoma cells. Conclusions: We conclude that Gen may be effective for the prevention of hypoxic PH through the improvement of PI3K/Akt-dependent NO-mediated signaling in association with enhancement of the EPO/EPOR system.