Background: Stroke is a leading cause of morbidity and mortality worldwide. Early severity assessment is essential for accurate prognosis and effective management. Inflammation plays a critical role in ischemic brain injury, and the neutrophil-lymphocyte ratio (NLR) is recognized as a straightforward and cost-effective biomarker. Objective: To assess the relationship between neutrophil-to-lymphocyte ratio (NLR) and stroke severity, as measured by the National Institutes of Health Stroke Scale (NIHSS), in individuals diagnosed with acute ischemic stroke. Methods: This prospective study included 120 consecutive patients experiencing their first acute ischemic stroke, all admitted within 72 hours of symptom onset. The neutrophil-to-lymphocyte ratio (NLR) was determined from blood samples collected at admission. Stroke severity was evaluated using the National Institutes of Health Stroke Scale (NIHSS). The relationship between NLR and NIHSS scores was examined using Pearson correlation coefficients and regression analyses. Results: Among the 120 patients studied, 65 (54.2%) exhibited a low neutrophil-to-lymphocyte ratio (NLR) below 3, whereas 55 (45.8%) had an elevated NLR above 3. Patients with elevated NLR showed significantly higher National Institutes of Health Stroke Scale (NIHSS) scores, indicating greater stroke severity (11.37 ± 4.76 compared to 5.21 ± 2.68; p < 0.01). There was a strong positive correlation between NLR and NIHSS (r = 0.57, p < 0.0001). Regression analysis identified NLR as an independent predictor of stroke severity. Conclusion: Elevated neutrophil-lymphocyte ratio (NLR) is significantly associated with increased National Institutes of Health Stroke Scale (NIHSS) scores in patients with acute ischemic stroke. Given its accessibility and low cost, NLR represents a valuable biomarker for early risk stratification and management of individuals experiencing ischemic stroke.