Pulmonary arterial hypertension (PAH) is a severe and progressive disease that causes right heart failure. The pathogenesis of PAH is generally characterized by persistent high pulmonary arterial resistance and pulmonary arterial remodeling. We recently showed that Eucommia ulmoides oliver leaf extract (ELE) improve right ventricular systolic pressure (RVSP) and pulmonary vessel muscularization. In the present study, we investigated the effects of geniposidic acid, a major component of ELE, on hypoxia-induced PAH in mice. 8-weeks-old male C57BL/6J mice were orally administered geniposidic acid (～1 mg/kg, ～5 mg/kg) during exposure to hypoxia for 4 weeks. Geniposidic acid significantly suppressed the elevation of RVSP in hypoxia-induced PAH mice. In addition, hypoxia-induced pulmonary arterial muscularization was tended to be attenuated in geniposidic acid-treated mice. In human pulmonary artery smooth muscle cells (HPASMC), endothelin-1-induced increase of intracellular Ca²⁺ was attenuated by geniposidic acid (200 µM). Furthermore, geniposidic acid (50 – 200 µM) increased the maximal respiration in HPASMC. Our findings suggest that geniposidic acid may effectively improve the development of hypoxia-induced PAH by preventing the vascular remodeling and mitochondrial dysfunction of pulmonary artery.