Hospitals have demonstrated their enormous capacity to adapt to the rapidly changing situation imposed by the pandemic: increasing the number of intensive care units and intermediate and inpatient beds, with the corresponding human resources, services and facilities required. Internationally, the enormous demand to manage the COVID-19 pandemic has challenged hospitals in terms of staffing, supplies and equipment. This article analyses the effect of the COVID-19 pandemic on hospital activities, from the perspective of its environmental impact. It compares a year of normal hospital activities, 2019, with data on hospital activities from 2020. The aim of this research is to analyse the changes produced by the pandemic in the regular activities of the hospital and to determine the environmental impact, which allows reflecting on the exceptional situation generated. The results show that the hospital’s environmental impact increased significantly in 2020 compared to 2019, with a 17.2% increase in overall environmental efficiency indices. The main contributors to this increase were waste generation and medical gas consumption, which are critical aspects of hospital activities during the pandemic.