Background Disaster scenarios challenge both novice and experienced nurses to navigate complex ethical dilemmas in resource-limited environments. Traditional nursing education often leaves new nurses unprepared for the ethical demands of disaster nursing. Utilitarianism must often guide triage ethics and decision-making. There is a critical need to equip nursing students with these ethical competencies. Research question/Aim This study explores nursing students’ lived experiences using introductory triage ethics in mass casualty incident simulation (MCIS). Research design A qualitative, interpretive phenomenological approach was employed, (...) analyzing reflective journal responses from senior nursing students following MCIS participation. Participants and research context Participants were senior-year nursing students from a private university in the U.S., engaging in MCIS as part of their curriculum, which simulated resource-limited disaster scenarios requiring real-time ethical decisions. Ethical considerations The study received Institutional Review Board (IRB) approval, and participants provided informed consent. Data were anonymized and did not affect academic evaluation. Findings Two major themes emerged: 1. Living in Ethical Dilemmas (subthemes: We Could Have Saved Them If…, Looking Past Obvious Suffering, How Can We Be Prepared?, We Can’t Abandon Them). 2. Development of Ethical Competency (subthemes: Knowing You’ve Done Enough, Finding New Perspectives, There Is No Right Answer). Students grew in moral reasoning and emotional resilience, transitioning from patient-centered care to utilitarian decision-making. Conclusions Participation in the mass casualty incident simulation allowed nursing students to confront and navigate complex ethical challenges in real time, fostering significant growth in moral reasoning and emotional resilience. Through immersion in simulated ethical dilemmas, students grappled with the tension between patient-centered care and the realities of utilitarian decision-making. This experience catalyzed a deeper understanding of ethical ambiguity and the development of moral clarity, equipping them with foundational skills for ethically navigating crises. Nursing curricula should recognize and incorporate opportunities that facilitate this ethical growth through experiential learning. (shrink)