A 61-year-old male with a history of hypertension presented to the emergency department with a severe, atypical headache without a history of trauma. The patient was neurologically intact, Hunt and Hess grade II, with an initial blood pressure of 172/96 mmHg. Computed tomography (CT) and subsequent computed tomography angiography (CTA) demonstrated diffuse SAH, contained largely within the basilar cisterns, but without clear source of the hemorrhage on CTA. Subsequent digital subtraction angiography (DSA) and digital rotational angiography (DRA) demonstrated a 3.5 mm idiopathic pseudoaneurysm projecting posteriorly from the basilar summit/posterior cerebral artery junction without evidence of arterial dissection []. Subsequent imaging both with CTA and DSA/DRA demonstrated decreased size and flow associated within the aneurysm. Expectant management of the aneurysm was undertaken and no subsequent treatment was administered. The patient had an expected course in the intensive care unit (ICU), including temporary ventricular drainage, and was discharged home in neurologically intact in stable condition. Follow-up DSA and DRA 14 days after hemorrhage demonstrated complete resolution of the pseudoaneurysm []. Subsequent follow-up, including imaging at 1 year, confirms the spontaneous and complete resolution.