Pseudoaneurysm of the superficial temporal artery must be considered in the differential diagnosis of masses of the lateral forehead and temporal fossa. While the first reported case of a temporal artery aneurysm was reported by Thomas Bartholin in 1740, there is scant mention of this lesion in the plastic and maxillofacial surgical literature. Pseudoaneurysms can arise in the forehead and scalp as a result of blunt traumatic impingement of the superficial temporal artery against the calvarium. The anterior branch of the artery is most vulnerable, because in the lateral forehead it courses over the frontal osseous ridge in the galea aponeurotica formed by the fusion line of the deep and superficial temporalis muscle fascia. This dense fascial investment has a tethering effect in the gap between the temporalis and frontalis muscles and prevents the artery from displacing laterally in response to traumatic forces. A history of recent blunt trauma or surgery to the forehead, combined with a pulsatile bruit, should direct the physician to the diagnosis of pseudoaneurysm of the superficial temporal artery. Treatment is surgical resection of the involved segment without the need for reconstruction. This report includes a review of the literature and presents the first documented case of a bicycle helmet as the cause of a superficial temporal artery pseudoaneurysm.