Pulmonary arterial hypertension is still a fatal disease persisting with poor prognosis, despite all the advances in treatment (new agents and new combination strategies) in recent years. Patients present with different symptoms which are not specific to the disease (dyspnea, angina, palpitation, and syncope). Angina may occur secondary to myocardial ischemia due to increased right ventricular after load (oxygen supply and demand mismatch) or external compression on the left main coronary artery. Left main coronary artery compression is associated with post-exercise sudden cardiac death in pulmonary arterial hypertension patients. It should be kept in mind in the differential diagnosis of angina in patients with pulmonary arterial hypertension and should be treated immediately. Here, we report a pulmonary arterial hypertension patient associated with secundum-type atrial septal defect presented with ostial left main coronary artery compression caused by an enlarged pulmonary artery and treated with intravascular ultrasound-guided percutaneous coronary intervention.