A simulation is a powerful tool for having an experience in a controlled and safe environment. In education, it has been used within simulation centers. The current study examined the effect of simulations on the professional self-efficacy of school principals in training. Twenty-two master of education students were asked to fill out the Principal's Professional Self-Efficacy Questionnaire before and after taking a course at a simulation center. Results showed a statistically significant increase in all five categories of professional SE. Strong positive correlations were found between the age of the students and each of the measured elements of professional SE in the post-test. Simulations within an organized, supervised process in a simulation center are a powerful tool for the professional development of principals in training.