Purpose: The literature indicates that sudden key experiences induce emotional and cognitive reactions strong enough to change perceptions and behavior over time. The purpose of this paper is to examine the question whether school principals undergo key experiences and whether these experiences are related to improvements in their work patterns and to professional empowerment beyond what could be attributable to the professional insights acquired through on-the-job experience. Design/methodology/approach: Qualitative in-depth interviews of 15 public high school principals with 4-19 years of experience elicited information about the extent of their exposure to key experiences and any changes that occurred in their managerial thinking and functioning after having undergone these experiences. Findings: All of the respondents implemented significant changes in their work after undergoing key experiences. The insights gained from key experiences had not been acquired through on-the-job experience. Nevertheless, the qualitative nature of this research does not allow for any conclusive findings about the causality of key experiences upon managerial changes among principals. Practical implications: It may be possible to use the findings uncovered by this study and its conclusions regarding experiential learning acquired from key experiences by school principals to enrich managers in general. Originality/value: This study demonstrates that the process of school principals' professional development involves a unique component and source of knowledge resulting from key experiences, and this phenomenon has not previously been investigated. This study's findings about key experiences contribute to a deeper understanding of the process of professional development among principals.