Purpose: The aim of this study was to investigate the relationship between repolarization parameters and National Institutes of Health Stroke Scale (NIHSS) score in patients with acute ischemic stroke. Materials and Methods: The study comprised 97 patients (males, 42; females, 55; 65 ± 16 years) with acute ischemic stroke. 17 patients were excluded. Patients were divided into two groups based on the calculated NIHSS score (Group 1, NIHSS score < 16; Group 2, NIHSS score ≥ 16). Demographic, clinical, and laboratory data for all patients were collected. A 12-lead resting ECG was recorded at admission to the neurology care unit in patients with acute ischemic stroke and were manually measured with a ruler. QTc, QTd, QTcd, Tpe, Tpe/QT parameters were measured. Results: There were no significant differences among demographic parameters of patients. We found that QTc, QTd, QTcd, Tpe, Tpe/QT parameters were significantly higher in Group 2 than Group 1 patients. Conclusion: In this study, we found that acute ischemic stroke has been shown to cause changes in repolarization parameters. Repolarization parameters are associated with stroke severity on admission in patients with acute ischemic stroke. Increased dispersion of repolarization parameters make independent contributions to the risk of arrhythmic cardiac death in patients with acute ischemic stroke. We suggested that especially severe ischemic stroke patients closely using cardiac monitoring during the first 24 h.