BACKGROUND:Anxiety has a powerful impact on learning due to activation of anxiety hormones, which target related receptors in the working memory. Experiential learning requires some degree of challenge and anxiety. Patient simulation, as a form of experiential learning, has been an integrated component of health professional education internationally over the last two decades, especially in undergraduate nursing education. Little information is available to determine if and how anxiety impacts nursing students' clinical performance during simulation. OBJECTIVES:To investigate physiological and psychological anxiety during emergency scenarios in high-fidelity simulation and understand the effect of anxiety on clinical performance. DESIGN:First2Act was the model for the simulation intervention. Second and third year undergraduate nursing students attended a two-hour simulation session and completed a demographic questionnaire plus pre-simulation self-reported psychological anxiety scale. A heart rate variability monitor was attached to each student's chest to measure heart rate variability (as a sign of anxiety) before engaging in two video-recorded simulated emergency scenarios (cardiac and respiratory) with a professional actor playing the patient. Performance was rated by a clinician followed by video-assisted debriefing. Finally, heart monitors were removed and students repeated self-reports of psychological anxiety. RESULTS:Students' psychological anxiety was high pre-simulation and remained high post-simulation. With regard to physiological anxiety, students were anxious at the start of the simulation but became more relaxed toward the end as they gained familiarly with the simulation environment (p < .007). Clinical performance increased significantly in the second scenario (p < .001). Factors found to positively affect clinical performance were length of enrolment in the nursing degree (p = .001), current employment in a nursing or allied healthcare field (p = .030), and previous emergency experience (p = .047). The relationship between physiological anxiety and clinical performance was statistically not significant, although there was an indication that low level anxiety led to optimal performance. CONCLUSION:High-fidelity patient simulation has the capacity to arouse novice nurses psychologically and physiologically while managing emergency situations. Indicative outcomes suggest that optimal performance was apparent when anxiety levels were low, indicating that they had received insufficient training to deal with situations that induced moderate to high anxiety levels.