The severity of neurological disorders in ischemic stroke (IS) in the presence of atrial fibrillation (AF) is known to be higher than that in patients with sinus rhythm. The impact of preventive antithrombotic therapy (ATT) on the clinical manifestations and outcomes of stroke remains a matter of debate.Objective: to analyze the quality of preventive ATT and to clarify its relationship to the severity of IS in AF.Patients and methods. The data from the registry of patients (n = 200; 96 (48%) men) (mean age, 71±9 years) with IS and AF were analyzed. Neurological deficit at admission was graded using the National Institutes of Health Stroke Scale (NIHSS). The presence and nature of prestroke antithrombotic therapy were studied.Results and discussion. Prestroke ATT was performed in 80 (40%) patients, of whom 36 (18%) took antiplatelet agents (APAs). Oral anticoagulants (OACs) were given to 44 patients. The international normalized ratio (INR) in the use of vitamin K antagonists (VKAs) averaged 1.26 [1.11; 1.64]. Neurological deficit was most obvious in the patients who had not previously received ATT (a NIHSS score of 8 [5; 12]). In comparison with them, the regular use of ATT, including APAs and OACs, was associated with the greater likelihood of less severe neurological deficit (a NIHSS of <8): odds ratio (OR), 2.121; 95% confidence interval (CI), 1.178–3.820. The greatest decrease in stroke severity was related to direct (OACs) (DOACs): OR, 2.727 (95% CI, 1.049–7.089), while there was no positive effect of VKAs (OR, 1.534; 95% CI, 0.538–4.377), which was associated with failure to achieve the INR target. Improvement was also related to the prescription of APAs (OR, 2.111; 95% CI, 0.981–4.539).Conclusion. Preventive ATT for a significant proportion of AF patients does not meet the current recommendations. At the same time, ATT, especially that with DOACs, is associated with the lesser severity of IS.