The necessity of disaster preparedness among nursing students has been continuously emphasized.This study aimed to verify the effectiveness of a simulation-based education program for nursing students responding to mass casualty incidents (MCI) from the perspectives of triage accuracy, response attitude, teamwork, and program satisfaction.This study employed a pre-post intervention design.Disaster Simulation Lab and a debriefing room in the University Nursing Simulation Center in South Korea.The participants were 34 graduating nursing students attending a university in Seoul.The program consisted of lectures on disaster nursing, group discussions, practice, debriefings, and a pre- and post-test, conducted over 180 min. Simulation-based training was conducted using the Emergo Train System®. The simulation environment comprised pre-hospital and hospital sections, with videos displayed on a large screen and sound effects played on loudspeakers.Participants were likely to undertriage. There was a significant increase in positive attitudes after the intervention (p < .001). Self-reported teamwork was high, and among its subfactors, "leadership and team coordination" scored the highest. Participants' satisfaction with the program was high (4.5/5.0).The simulation-based MCI program was effective in boosting positive attitudes among nursing students. In future, comparative studies including control groups and different instructional methods should be conducted. A patient bank should also be developed considering participants' knowledge levels and the circumstances of each country.