Purpose: This study aimed to compare students’ and examiner’s assessment scores of students’ simulated performance. Methods: For two years, 46 teams of 183 senior nursing students participated in simulated emergency. The examiner assessed the students’ reactions during simulation using the Nursing Competency Scale in Simulation (NCSS). The students assessed their own performance using the same scale after participating in the simulation. Data were analyzed using descriptive statistics, a paired t-test, a one-way ANOVA, a Kruskal-Wallis test, an independent t-test, and a Mann-Whitney U test. Results: The students’ NCSS scores were significantly higher than those of the examiner. The difference of students’ self-rated and examiner’ scores was larger in the lower third group of actual NCSS scores as compared to the difference for those in the upper third group. The students’ self-assessment accuracy improved after exposure to the NCSS, but the change was not significant. Conclusion: The findings can be suggest various strategies to promote more realistic self-appraisals among students.