Background: Spain was one of the most affected countries during the first wave of COVID-19, having the highest mortality rate in Europe. The aim of this retrospective study is to estimate the impact that remdesivir -the first drug for COVID-19 approved in EU- would have had in the first wave. Methods: This study estimated the impact on the Spanish National Health System (SNHS) capacity (bed occupancy), and the number of deaths that could have been prevented, based on two scenarios: a real-life scenario (without remdesivir), and an alternative scenario (with remdesivir). It considered the clinical results of the ACTT-1 trial in hospitalized patients with COVID-19 and pneumonia, who required supplemental oxygen. The occupancy rates in general wards and ICUs were estimated in both scenarios. Results: Remdesivir would have avoided the admission of 2,587 patients (43.75%) in the ICUs. It would have also increased the SNHS capacity in 5,656 general wards beds and 1,700 ICU beds, showing an increase in the number of beds available of 17.53% (95% CI: 3.98% - 24.42%), and 23.98% (95% CI: 21.33% - 28.22%), respectively, at the peak of the occupancy rates. Furthermore, remdesivir would have avoided 7,639 deaths due to COVID-19, which implies a 27.51% reduction (95% CI: 14.25% - 34.07%). Conclusions: Remdesivir would have relieved the pressure of the SNHS, and would have reduced the death toll, providing a better strategy for the management of COVID-19 during the first wave.