INTRODUCTION: CHA2DS2-VASc and CHA2DS2-VA scores are often used to demonstrate thromboembolic risk in nonvalvular atrial fibrillation. Elevated whole blood viscosity is an independent risk factor for ischemic stroke. OBJECTIVE: This study aimed to ascertain the correlation between whole blood viscosity and CHA2DS2-VASc/CHA2DS2-VA scores. METHODS: This study was performed retrospectively in a tertiary cardiac facility, encompassing 150 patients. RESULTS: The study's results demonstrate that whole blood viscosity, concerning both high shear rate and low shear rate variables, are statistically significant in forecasting the likelihood of elevated CHA2DS2-VA and CHA2DS2-VASc scores. CONCLUSION: Whole blood viscosity had a substantial correlation with the CHA2DS2-VASc/CHA2DS2-VA scores in patients with atrial fibrillation and may be used to evaluate thromboembolism risk, akin to these scores.