(1) Background: The COVID-19 pandemic has led to an increase in the complexity of caregiving, resulting in challenging situations for perioperative nurses. These situations have prompted nurses to assess their personal and professional lives. The aim of this study was to explore the experiences of perioperative nurses during the first wave of the COVID-19 pandemic, with a specific focus on analyzing moral breakdowns and ethical dilemmas triggered by this situation. (2) Methods: A qualitative design guided by a hermeneutical approach was employed. Semi-structured interviews were conducted with 24 perioperative nurses. The interviews were transcribed and thematically analysed following the Consolidated Criteria for Reporting Qualitative Research (COREQ) guidelines. (3) Results: The findings revealed three main categories and ten subcategories. These categories included the context in which moral breakdowns emerged, the ethical dilemmas triggered by these breakdowns, and the consequences of facing these dilemmas. (4) Conclusions: During the first wave of COVID-19, perioperative nurses encountered moral and ethical challenges, referred to as moral breakdowns, in critical settings. These challenges presented significant obstacles and negatively impacted professional responsibility and well-being. Future studies should focus on identifying ethical dilemmas during critical periods and developing strategies to enhance collaboration among colleagues and provide comprehensive support.