Ultrasound-guided fine needle aspiration biopsy (USFNA) is a very useful procedure for the diagnosis and management of thyroid diseases. It is very safe procedure and complications have been rarely reported. We experienced a case of an extensive hemorrhage after USFNA of the thyroid nodule in a patient undergoing long-term aspirin therapy. We emphasize that it is very important to obtain a patient history carefully before performing a USFNA.