Hypereosinophilic syndrome is a myeloproliferative disorder characterized by persistent eosinophilia with involvement of multiple organs. The occurrence of severe pulmonary hypertension (PH) in the setting of hypereosinophilic syndrome is very uncommon. A 43-year-old man with documented idiopathic hypereosinophlic syndrome presented to the hospital with symptoms of paroxysmal chest discomfort and progressive exertional dyspnea. Physical examination showed distended jugular veins, cyanosed lips, increased P2 sound, and moderate pitting edema of the lower extremities. Echocardiography revealed enlarged right atrium, enlarged right ventricle, increased pulmonary artery systolic pressure, and decreased right ventricular systolic function. Venous ultrasound of the lower extremities, computed tomography pulmonary angiography, and right heart catheterization (RHC) were negative for thrombus. The pulmonary artery systolic pressure was found severely increased during the RHC. Treatment included prednisolone, ambrisentan, diuretics, and digoxin. The involvement of the pulmonary artery in patients with idiopathic hypereosinophilic syndrome is an uncommon finding. The patient presents with clinical manifestations of right ventricular systolic dysfunction resulted from severely increased PH.