Background: This study aimed to evaluate the impact of tocilizumab treatment on clinical improvement in severe COVID-19 cases and the factors affecting clinical response.Methods: This single-center, retrospective, descriptive study was conducted on severe COVID-19 patients. The ordinal scale of clinical status scores on the 0th, 1st, 3rd, and 7th days of tocilizumab treatment was calculated and compared for each patient. The ordinal scale of clinical status scores calculated on different days for the same patient was compared with Wilcoxon tests. The correlation between the clinical score and some laboratory parameters was evaluated by Pearson correlation analysis. Patients were grouped as responders and non-responders and compared by logistic regression analysis.Results: Forty-two patients were enrolled in the study. The median of the ordinal scale of clinical status scores on the 0th, 1st, 3rd, and 7th days of tocilizumab treatment were 6 (5 to 6), 6 (5 to 6), 6 (5 to 6), and 5 (4 to 7), respectively. When the clinical status scores on the 0 to 7 days of tocilizumab treatment were compared, the difference was statistically significant (p = 0.024, Wilcoxon). There was no statistically significant difference between day 0 and day 1 (p=0.317, Wilcoxon), day 0 and day 3 (p=0.467, Wilcoxon). By multivariate analysis, we determined that age ( OR: 0.91, 95% 0.84-0.98) and respiratory rate (OR:0.78, 95% 0.62-0.98) were factors affecting the response of tocilizumab treatment. No relationship was detected between laboratory parameters before tocilizumab treatment, including IL-6 levels and clinical response (p=0.756, Mann Whitney-U).Conclusion: The use of tocilizumab in younger patients with low oxygen support increases the chance of clinical response after treatment. Since the effect of laboratory parameters in predicting the clinical response of tocilizumab is limited, treatment indications should be determined based on clinical parameters.