Background. Thyroid storm is a well-known complication of surgical procedures in the lower neck, but is rare after a blunt neck trauma. The cases described previously have mainly focussed on adults with pre-existent thyroid disease. In this case report, we describe the disease course of a previously healthy adolescent who had asymptomatic hyperthyroxinemia after a blunt trauma of the jaw and neck. Case Presentation. A 17-year-old girl presented at our emergency department after she fell on her head while roller blading. On physical examination, among other injuries, she had a swelling in the lower neck, which appeared to involve the thyroid gland. Subsequent laboratory analysis was indicative of primary hyperthyroxinemia, with a free T4 of 59 pmol/L (reference range: 12-22) and a TSH of 0.46 mU/L (reference range: 0.5-4.3), but the patient had no symptoms fitting with this. Four weeks after the initial presentation, the patient reported only complaints regarding tenderness in the jaw and neck region. She was no longer hyperthyroidic on biochemical evaluation (with a free T4 level of 15.6 pmol/L and a TSH level of 0.33 mU/L), and antibodies against thyroid peroxidase or TSH receptor were not present. Conclusions. This case might indicate that hyperthyroxinemia following a neck trauma may go unnoticed if hyperthyroid symptoms are mild or absent and thyroid function tests are not performed.