Background: Remdesivir is a prodrug with in vitro activity against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Its clinical efficacy in patients with COVID-19 under mechanical ventilation remains to be evaluated. Methods: This study includes patients under mechanical ventilation with confirmed SARS-CoV-2 infection admitted to the ICU of Pesaro hospital between 29 February and 20 March 2020. During this period, remdesivir was provided on a compassionate use basis. Clinical characteristics and outcome of patients treated with remdesivir were collected retrospectively and compared with those of patients hospitalized in the same time period. Results: A total of 51 patients were considered, of which 25 were treated with remdesivir. The median (IQR) age was 67 (59-75.5) years, 92% were men and symptom onset was 10 (8-12) days before admission to ICU. At baseline, there was no significant difference in demographic characteristics, comorbidities and laboratory values between patients treated and not treated with remdesivir. Median follow-up was 52 (46-57) days. Kaplan-Meier curves showed significantly lower mortality among patients who had been treated with remdesivir (56% versus 92%, P < 0.001). Cox regression analysis showed that the Charlson Comorbidity Index was the only factor that had a significant association with higher mortality (OR 1.184; 95% CI 1.027-1.365; P = 0.020), while the use of remdesivir was associated with better survival (OR 3.506; 95% CI 1.768-6.954; P < 0.001). Conclusions: In this study the mortality rate of patients with COVID-19 under mechanical ventilation is confirmed to be high. The use of remdesivir was associated with a significant beneficial effect on survival.