Pulmonary hypertension (PH) is a chronic vascular disease characterized by elevated pulmonary arterial resistance and vascular remodeling, and chronic hypoxia plays an important role in PH. Milk fat globule-EGF factor 8 (MFG-E8) is a glycoprotein that regulates cell proliferation and apoptosis, but its role in hypoxia-induced PH is unknown. The current study aimed to determine the function and fundamental mechanisms of MFG-E8 in hypoxia-induced PH. Herein, we exposed mice to hypoxia for 5 weeks, and MFG-E8 was found to be elevated in mouse lung tissues, arteries, and plasma. Compared with wild-type littermates, mice lacking MFG-E8 showed a significant increase in the ratio of pulmonary artery acceleration time to ejection time (PAT/PET), while they showed decreases in right ventricular systolic pressure, the Fulton's Index, percent medial wall thickness (%WT), and vascular muscularization in pulmonary arteries. In addition, MFG-E8 protein levels were also increased in the serum of patients with chronic PH. Similarly, we observed a higher expression of MFG-E8 in human pulmonary artery smooth muscle cells (PASMCs) in the presence of hypoxic stimulation than MFG-E8 in cells in normoxic conditions. Furthermore, MFG-E8 silencing resulted in partial inhibition of proliferation, migration and cell cycle progression in human PASMCs, and the possible mechanisms might involve the interaction between MFG-E8 and the p-Akt/cyclin D1 pathway. Collectively, our study suggests that the absence of MFG-E8 can attenuate the development of hypoxia-induced PH and vascular remodeling. MFG-E8 can be a potential therapeutic target or a biomarker for PH.