The treatment of unruptured intracranial aneurysms remains controversial. The PHASES score was developed to predict the 5-year risk of aneurysm rupture. We have assigned PHASES scores to a cohort of aneurysmal subarachnoid hemorrhage (aSAH) patients to assess the distribution of scores and its ability to predict outcome. In this study, the PHASES score was applied to a prospective cohort of aSAH patients that were enrolled in the Cerebral Aneurysm Renin Angiotensin System (CARAS) study. The CARAS study enrolled patients from two academic institutions in the United States from 2012 to 2015. Univariable and multivariable analyses were performed to identify factors predictive of outcome at last follow up. One hundred and forty-nine aSAH patients were included with a mean age of 54.9 ± 12.5 years. Most ruptured aneurysms were <7 mm (62.4%) and located in the anterior circulation (80.5%). Favorable functional outcome (mRS 0–2) at last follow up was achieved in 61.7% of patients. PHASES scores ranged from 0 to 16 with a median of 5; the majority of patients had a score of 4 (20.1%) or 5 (32.2%). Multivariable modeling identified higher PHASES scores (OR 1.235, CI 1.016–1.501, p = 0.034) and higher Hunt and Hess grades (OR 2.224, CI 1.353–3.655, p = 0.002) as independent predictors of poor functional outcome (mRS 3–6) at last follow up. The majority of aSAH patients present with low (≤5) PHASES scores. Elevated PHASES scores are independently associated with poor functional outcome in patients with aSAH.