Although essential thrombocythemia (ET) has been rarely reported to cause coronary thrombosis, its appropriate management is still undefined. We describe a case of acute coronary syndrome in a patient with ET. A 47-year-old woman with ET complained of severe acute chest pain. Primary coronary angiography showed severe stenosis with thrombus in the proximal left anterior descending coronary artery. The patient was treated with anti-platelet drugs and hydroxyurea to prevent in-stent thrombosis, and subsequently underwent successful coronary angioplasty using aspiration and a distal protection device without thrombotic coronary complications.