Introduction: The COVID-19 pandemic caused an international health emergency situation where nursing took on a fundamental role. The high number of patients in hospital ICUs led to a shift in nurses’ working conditions and workload. Objective: The objective of this study was to describe the experiences of nurses who worked in ICUs during the acute phase of the COVID-19 pandemic. Methodology: A qualitative, descriptive study was carried out, with the participation of 21 nurses who worked in the ICU during the pandemic. Data collection took place between May and July 2021 through 21 in-depth interviews. Results: Three main themes emerged: (1) COVID-19 in ICUs: nurses on the frontline. (2) United against adversity: teamwork. (3) New optics of critical care and the nursing profession. COVID-19 was perceived with harshness, and the lack of knowledge about the virus generated confusion, anxiety and fear due to the risk of transmission to family members and relatives. The pandemic marked a shift in the management of human, material and economic resources. Novice nurses learned critical care at an accelerated pace, with significant physical and psychological strain. Expert nurses carried the burden of training new nurses. Although there were tense situations, experiencing these adverse situations as a team led to feelings of increased belonging, togetherness and professional bonding for nurses. While the participants noted an increase in motivation to continue in their profession, they also had a feeling of not having been cared for as they deserve by healthcare institutions. © 2024 by the authors.Universidad de Almería, UAL, (CTS-451)