Objective: Cognitive deficits are common after aneurysmal subarachnoid haemorrhage (aSAH), and clinical evaluation is important for their management. Our hypothesis was that the Montreal Cognitive Assessment (MoCa) is superior to the Mini-Mental State Examination (MMSE) in screening for cognitive domain deficit in aSAH patients. Methods: We carried out a prospective observational and diagnostic accuracy study on Hong Kong aSAH patients aged 21 to 75 years who had been admitted within 96 hours of ictus. The domain-specific neuropsychological assessment battery, the MoCA and MMSE were administered 2–4 weeks and 1 year after ictus. A cognitive domain deficit was defined as a cognitive domain z score <−1.65 (below the fifth percentile). Cognitive impairment was defined as two or more cognitive domain deficits. The study is registered at ClinicalTrials.gov of the US National Institutes of Health (NCT01038193). Results: Both the MoCA and the MMSE were successful in differentiating between patients with and without cognitive domain deficits and cognitive impairment at both assessment periods. At 1 year post-ictus, the MoCA produced higher area under the curve scores for cognitive impairment than the MMSE (MoCA, 0.92; 95% CI, 0.83 to 0.97 versus MMSE, 0.77; 95% CI, 0.66 to 0.83, p = 0.009). Interpretation: Cognitive domain deficits and cognitive impairment in patients with aSAH can be screened with the MoCA in both the subacute and chronic phases. Copyright © 2013 Wong et al.