Objective: What we know about the relationship between oxidative stress parameters and ischemic stroke is still limited and controversial. Our study aimed to investigate the relationships among ischemic lesion volume, National Institutes of Health Stroke Scale (NIHSS) values, and oxidant and antioxidant levels to determine whether oxidative stress paramaters is effective on stroke severity in ischemic stroke patients. Methods: The study included 34 patients with ischemic stroke and 34 volunteers with no active diseases. Total Oxidant Status (TOS), Total Antioxidant Status (TAS), thiol, paraoxonase, stimulated paraoxonase (stparaoxonase) and arylesterase were measured in blood samples collected on admission from patients diagnosed with ischemic stroke. The Oxidative Stress Index (OSI) was calculated. The same oxidative stress parameters were measured in the control group and compared with the patient group. Correlation between the oxidative stress parameters, the infarct volume and the NIHSS was studied. NIHSS was calculated when patients were admitted to the emergency department. The infarct volume was calculated using diffusion-weighted magnetic resonance imaging performed in the first 72-96 hours. Results: TOS and OSI values were significantly higher in the case group than the control group. Paraoxonase, arylesterase, and thiol values were significantly lower in the case group than the control group. TAS and stparaoxonase values weren’t differed significantly between the case and control groups. There were significant negative correlations between the NIHSS value and both the paraoxonase value and stparaoxonase value. There were no significant correlations between the NIHSS value and the infarct volume and the TAS, TOS, OSI, arylesterase, and thiol values. Conclusion: We concluded that change in oxidative stress balance in favor of oxidants could be a cause in the pathogenesis of ischemic stroke but oxidative stress alone can’t be sufficient in predicting the severity of stroke.