Pseudoaneurysm of the superficial temporal artery (STA) is a rare clinical entity that has been linked with traumatic causes. Neurofibromatosis type I (NF-1) is an autosomal dominant disorder with known but uncommon vascular abnormalities that comprise stenoses, occlusions, aneurysms, fistulas and arteriovenous malformations. We presented a 46-year-old man with clinical features of NF-1 (e.g., café au lait spots, skin neurofibromas) coming to hospital because of a progressively enlarging and painful right temporal mass of about ping-pong ball size. He remembered having slapping a mosquito with his hands at the same area four days ago. CT angiography suggested development of a pseudoaneurysm and emergency surgery was performed to dissect the mass. Histopathological examination revealed disruption of arterial wall structures, including interruption of elastic lamina, expansion of smooth muscle layer, focal thrombosis and positive CD31 and smooth muscle actin staining, consistent with diagnosis of pseudoaneurysm. This is the first report of a STA pseudoaneurysm in patient with NF-1. Deficiency of neurofibromin may impact the integrity of vascular wall structures and predispose it to the development of pseudoaneurysm in the event of minor trauma like current case. Reference 1. Saliba E, Goldberg LJ. Superficial temporal artery pseudoaneurysm: report of two cases and review. J Cutan Pathol 2022; 49: 482–486.