Introduction: Atrial fibrillation (AF) is the most common heart arrhythmia. The condition is known to increase the risk of ischemic stroke (IS). Classical risk factors for the development of AF include advanced age, hypertension, diabetes mellitus, coronary heart disease and lipid metabolism disorders. Importantly, these are also recognized risk factors for ischemic stroke. Therefore, the purpose of this study was to investigate AF risk factors in patients with IS. Material and methods: This is single-centre retrospective study which included 696 patients with acute ischemic stroke and nonvalvular atrial fibrillation and 1678 patients with acute ischemic stroke without atrial fibrillation. Results: In this study we found-based on a univariable and multivariable logistic regression model-that compared to the patients with IS without AF, the group of patients which suffered from IS with nonvalvular atrial fibrillation (NVAF) had a higher proportion of patients who smoked cigarettes (OR = 15.742, p < 0.01; OR = 41.1, p < 0.01), had hypertension (OR = 5.161, p < 0.01; OR = 5.666, p < 0.01), history of previous stroke (OR = 3.951, p < 0.01; OR = 4.792, p < 0.01), dyslipidemia (OR = 2.312, p < 0.01; OR = 1.592, p < 0.01), coronary heart disease (OR = 2.306, p < 0.01; OR = 1.988, p < 0.01), a greater proportion of female patients (OR = 1.717, p < 0.01; OR = 2.095, p < 0.01), higher incidence of diabetes mellitus (OR = 1.341, p < 0.01; OR = 1.261, p = 0.106) and more patients in old age (OR = 1.084, p < 0.01; OR = 1.101, p < 0.01). Conclusions: Our study demonstrates a need for thorough and systematic monitoring of post-ischemic stroke patients in whom AF has not been detected and who display other important risk factors. Regardless of the stroke, these factors may be responsible for development of AF.