Background:Atrial fibrillation is a major risk factor for ischemic stroke. However, the prognostic impact of atrial fibrillation among patients with stroke is not fully clarified. We compared patient characteristics, including severity of stroke and comorbidity, quality of in-hospital care and outcomes in a cohort of first-time ischemic stroke patients with and without atrial fibrillation.Methods:Based on linkage of public medical databases, we did a population-based follow-up study among 3,849 stroke patients from the County of Aarhus, Denmark admitted in the period of 2003–2007 and prospectively registered in the Danish National Indicator Project.Results:Atrial fibrillation was associated with an adverse prognostic profile but not with an overall poorer quality of in-hospital care. Patients with atrial fibrillation had a longer total length of stay (median: 15 vs 9 days), and were at increased risk of in-hospital medical complications (adjusted relative risk = 1.48, 95% CI: 1.23–1.79) and recurrent stroke (adjusted hazard ratio = 1.30, 95% CI: 0.93–1.82) when compared with patients without atrial fibrillation. The adjusted hazard ratios for 30 days and one year mortality were 1.55 (95% CI: 1.20–2.01) and 1.55 (95% CI: 1.30–1.85), respectively. Patients not eligible to oral anticoagulant treatment had an increased risk of recurrent stroke (adjusted hazard ratio = 1.92, 95% CI: 1.19–3.11).Conclusion:Atrial fibrillation is associated with a poor outcome among patients with ischemic stroke particularly among patients, who are not eligible to oral anticoagulant treatment.