Background: Cognitive domain deficits can occur after aneurysmal subarachnoid haemorrhage (aSAH) though few studies systemically evaluate its impact on 1-year outcomes. Objective: We aimed to evaluate the pattern and functional outcome impact of cognitive domain deficits in aSAH patients at 1 year. Methods: We carried out a prospective observational study in Hong Kong, during which, 168 aSAH patients (aged 21–75 years and had been admitted within 96 h of ictus) were recruited over a 26-month period. The cognitive function was assessed by a domain-specific neuropsychological assessment battery at 1 year after ictus. The current study is registered at ClinicalTrials.gov of the US National Institutes of Health (NCT01038193). Results: Prevalence of individual domain deficits varied between 7% to 15%, and 13% had two or more domain deficits. After adjusting for abbreviated National Institute of Health Stroke Scale and Geriatric Depressive Scale scores, unfavourable outcome (Modified Rankin Scale 3–5) and dependent instrumental activity of daily living (Lawton Instrumental Activity of Daily Living<15) were significantly associated with two or more domain deficits and number of cognitive domain deficits at 1 year. Two or more domain deficits was independently associated with age (OR, 1.1; 95% CI 1.1 to 1.2; p<0.001) and delayed cerebral infarction (OR, 6.1; 95% CI 1.1 to 33.5; p=0.036), after adjustment for years of school education. Interpretation: In patients with aSAH, cognitive domain deficits worsened functional outcomes at 1 year. Delayed cerebral infarction was an independent risk factor for two or more domain deficits at 1 year. Copyright © 2013 by the BMJ Publishing Group Ltd.