Patients with atrial fibrillation (AF) are at a higher risk of thrombotic stroke. Therefore treatment with an oral anticoagulant (OAC) has been proven to prevent stroke, however, the bleeding side effect of OAC is the concern for both physicians and patients. Patients’ knowledge of the stroke and bleeding related to AF is lacking in Saudi Arabia. We conducted this study to assess the knowledge of patients on AF related to stroke and bleeding from OAC. Method: this is a cross-sectional study conducted in a tertiary care university center in Riyadh Saudi Arabia. A validated questioner provided to patients or patients’ relatives who were diagnosed as permanent AF on OAC, 15 years of age or older who consented to participate in answering the questionnaire. Results: Of 229 patients analyzed 46% were male and 54% were female; 58.8% in the age of 56-75 years. They were obese and had a sedentary lifestyle. 42% knew AF symptoms, 28.9% knew AF can cause stroke, 39% knew bleeding side effect of OAC and there were no gender differences. Conclusion: This study revealed poor knowledge about AF, stroke, and bleeding side effects, and this mandate urgent strategy for patients’ education in Saudi Arabia.