BACKGROUND Thyroid rupture following blunt trauma is extremely rare, and neck pain without swelling may be the only presenting symptom. However, hemorrhage and hematoma subsequently causes severe tracheal compression and respiratory distress. METHODS A 71-year-old Japanese woman visited our emergency room with a complaint of increasing right-sided neck pain at the thyroid cartilage level after she tripped and accidentally hit her neck against a pole 3 h back. On admission, her vital signs were stable. There was no swelling or subcutaneous emphysema. Laryngeal endoscopy revealed mild laryngeal edema, although there was no impairment in vocal fold mobility on either side. Contrast-enhanced computed tomography (CT) revealed rupture of the right lobe of the thyroid gland accompanied by a large hematoma extending from the neck to the mediastinum. Under general anesthesia, the right lobe was resected and the hematoma was evacuated. CONCLUSIONS Only a few isolated cases of thyroid rupture caused by blunt neck trauma have been reported in patients with normal thyroid glands and neck pain without swelling may be the only presenting symptom. When suspected, CT should be performed to confirm the diagnosis determine the optimal treatment.