Purpose: The purpose of this study was to evaluate the effects of mechanical ventilation simulation on the clinical judgment and self-confidence of nursing students. Methods: This study was a quasi-experimental study. From one university, 118 undergraduate nursing students participated in this study. Sixty students were in the intervention group, and fifty-eight students were in the control group. A simulation scenario utilizing a high-fidelity human simulator focusing on nursing care for patients with a mechanical ventilator was developed for this study. Data were collected with a self-report survey method before the intervention, right after intervention, and two weeks later. Results: Students in the intervention group showed significantly higher increases in clinical judgment and self-confidence than those in the control group at the immediate posttest. Moreover, 2 weeks later, the increase in clinical judgment and self-confidence from the pretest among the intervention group was significantly larger than those in the control group. Conclusion: Utilizing simulation education focusing on patients with a mechanical ventilator may contribute to training more competent nurses in the area of critical care nursing. It may also serve to provide a better critical care environment for the safety and health of patients.