Background and Purpose— Preadmission oral anticoagulant treatment (OAT) has been linked with less severe stroke and a better outcome in patients with atrial fibrillation. However, the existing studies have methodological limitations and have, with one exception, not included hemorrhagic strokes. We performed a nationwide historic follow-up study using data from population-based healthcare registries to assess the effect of preadmission OAT on stroke outcomes further. Methods— We identified 11 356 patients with atrial fibrillation admitted to hospital with acute stroke (including ischemic stroke and intracerebral hemorrhage) between 2003 and 2009. Propensity score–matched analyses were used to compare stroke severity (Scandinavian Stroke Scale score) and mortality among 2175 patients with preadmission OAT and 2175 patients without preadmission OAT. Results— A total of 2492 (21.9%) patients received OAT at the time of their stroke. Preadmission OAT was associated with a lower risk of severe stroke (Scandinavian Stroke Scale score at time of admission, <30 point; propensity score–matched odds ratio, 0.74; 95% confidence interval, 0.63–0.86) and lower 30-day mortality rate (propensity score–matched adjusted odds ratio, 0.83; 95% confidence interval, 0.71–0.98). Conclusions— Only a minority of hospitalized patients with acute stroke with atrial fibrillation received OAT at the time of stroke. Preadmission OAT was associated with less severe stroke and lower 30-day mortality rate in a propensity score–matched analysis.