A male cyclist presented with a swelling on the forehead. Six weeks before, he fell of his bike and smashed his head on the ground while wearing a helmet. A smooth lump of 1 cm had evolved on the temporal side of his forehead in a few weeks. Duplex ultrasonography demonstrated a dilated vessel with a minor defect in the luminal wall. Surgical exploration revealed an aneurysm of the superficial temporal artery (STA). The aneurysm was surgically removed and the patient recovered uneventfully. Owing to its superficial course, the STA is vulnerable to blunt head trauma. Traumatic aneurysms of the STA should be a differential diagnostic consideration in patients with a history of trauma and a swelling on their head.