<b><i>Background and Purpose:</i></b> Anticoagulant drugs, including vitamin K antagonist (VKA) and direct oral anticoagulants (DOACs), can reduce stroke severity and are associated with good functional outcomes. Some patients are prescribed lower-than-recommended doses of DOACs; whether these have similar effects has not been clarified. <b><i>Methods:</i></b> We retrospectively evaluated 1,139 consecutive ischemic stroke and transient ischemic attack patients with atrial fibrillation. Patients were divided into 5 groups according to their preceding anticoagulant drug therapies: no anticoagulant therapy (AC<sub>n</sub>), undercontrolling VKA doses (VKA<sub>uc</sub>), recommended, controlling VKA doses (VKA<sub>rec</sub>), prescribed underdoses of DOAC (DOAC<sub>ud</sub>), and recommended doses of DOAC (DOAC<sub>rec</sub>). We investigated the associations between these anticoagulant drug therapies and patients’ initial stroke severity and 3-month outcomes. <b><i>Results:</i></b> Median National Institutes of Health Stroke Scale scores at admission were as follows: AC<sub>n</sub>: 16, VKA<sub>uc</sub>: 15, VKA<sub>rec</sub>: 9, DOAC<sub>ud</sub>: 5, and DOAC<sub>rec</sub>: 7. When the AC<sub>n</sub> group was used as a reference, regression analysis showed that VKA<sub>rec</sub> (odds ratio [OR] 1.49, 95% confidence interval [CI] 1.01–2.21), DOAC<sub>ud</sub> (OR 2.84, 95% CI: 1.47–5.66), and DOAC<sub>rec</sub> (OR 1.83, 95% CI: 1.23–2.74) were associated with milder stroke severity, while VKA<sub>uc</sub> was not. Median 3-month modified Rankin Scale scores were 2 in the DOAC<sub>ud</sub> and DOAC<sub>rec</sub> groups and 4 in all other groups. After adjusting for confounding factors, DOAC<sub>ud</sub> (OR 3.14, 95% CI: 1.50–6.57) and DOAC<sub>rec</sub> (OR 1.67, 95% CI: 1.05–2.64) were associated with good 3-month outcomes while VKA<sub>uc</sub> and VKA<sub>rec</sub> were not. <b><i>Conclusions:</i></b> In patients with atrial fibrillation, recommended doses and underdoses of DOACs reduced stroke severity on admission and were associated with good 3-month outcomes.