Rationale: Cavernous internal carotid artery (ICA) pseudoaneurysm caused by non-penetrating head trauma is a rare cause of massive epistaxis. The sudden onset of epistaxis due to such a fatal aneurysm protruding into the sphenoid sinus is extremely rare in clinical practice. The management is often challenging because of anatomical inaccessibility of the bleeding point. Patient's concern: A 42-year-old man with a history of head trauma showing an ICA aneurysm eroding the sphenoid sinus followed by massive epistaxis. Diagnosis: A computerized tomography (CT) scan showed a fracture in the sphenoid sinus. CT angiogram revealed cavernous ICA pseudoaneurysm. Interventions: Endovascular coil embolization. Outcomes: The patient recovered well and was discharged without any neurological deficits Lessons: Cavernous ICA pseudoaneurysm may lead to a life-threatening situation. If a patient has a history of head trauma, post-traumatic cavernous ICA pseudoaneurysm should be considered a differential diagnosis of massive epistaxis.