Introduction: atrial fibrillation (AF) is characterized by disorganized, rapid and irregular atrial activation, with loss of atrial contraction and an irregular ventricular rate.Objective: determine the thromboembolic risk in patients with atrial fibrillation.Method: an observational, descriptive and cross-sectional investigation was carried out on patients treated with atrial fibrillation at the “Abel Santamaría Cuadrado” General Teaching Hospital, in the period January 2020 to January 2021. The study universe consisted of 93 patients diagnosed with said disease in the study period, of which 57 patients were selected through simple random sampling to make up the analyzed sample.Results: a predominance of the male sex was observed (56.1%), while the most represented age group was between 76 and 85 years of age (45.6%), moderate risk is the most frequent among patients with 59.6 % and 35.1% at serious risk of thromboembolism, the most frequent symptom is palpitations present in 53 cases (92.9%), followed by respiratory difficulty (71.9%), a high comorbidity is present, with arterial hypertension predominating in 47 cases ( 82.5%), followed by heart disease present in 63.1% of patients.Conclusions: AF is more common in elderly men, with HTN manifesting as the main associated disease and palpitations as the main symptom, reaching a moderate risk of thromboembolism in most cases.