Purpose: This study aimed to evaluate the effects of a simulation-based Room of Errors patient safety education program on patient safety-related nursing activities and critical reflection competency of new nurses. Method: A randomized controlled pretest–posttest design was used. A total of 63 new nurses participated, with 32 assigned to the experimental group and 31 to the control group. The experimental group received a team-based simulation intervention, with participants collaboratively identifying and addressing patient safety hazards within Room of Errors scenarios. Results: In the experimental group, patient safety-related nursing activity scores increased significantly after the intervention (t = 2.70, p = .011), while the control group showed no significant change (t = 0.23, p = .816). Additionally, critical reflection competency scores improved significantly in the experimental group (t = 3.66, p < .001), with no significant change observed in the control group (t = -0.53, p = .603). The between-group difference in change scores for critical reflection competency was statistically significant (t = 2.77, p = .007). Conclusion: The simulation-based Room of Errors education program effectively enhanced patient safety-related nursing activities and critical reflection competency among new nurses, suggesting its value as a training method for developing essential competencies in clinical practice.