Purpose : The purpose of this study is to explore and describe the immersion experiences of an comprehensive simulation scenario using high-fidelity human patient simulator. Methods : A phenomenological study was conducted. A total of 17 undergraduate senior students were recruited in a university in South Korea. Five to six students were exposed to a clinical scenario using a high-fidelity human patient simulator. Three students participated in a situation, and the others observed the simulation as observers. Qualitative data was collected through focus group interview technique. Three focus group interviews were conducted and each interview lasted about one and a half hours. Semi-structured questions were asked exploring their experiences as participants and observers in the simulation. All interviews were tape-recorded, transcribed, and analyzed according to van Manen`s phenomenological data analysis. Results : The results were developed into the 1 major theme with 6 sub-themes. The major theme of the study was "encountering a new world which is felt as real." The participants expressed that they encountered a new way of learning in which they felt as if it were real in clinical setting. Conclusion : The findings of the study demonstrated the effectiveness of simulated scenarios in providing realistic clinical experiences for undergraduate students. This implied that the tasks of nursing clinical education should be lied on how and what to be made as realistic as possible in nursing clinical education.