There is growing interest in the role that principals play as school leaders. Exploring how principals build their professional leadership identity is crucial to understanding their influence on school performance. A systematic review was conducted to examine how educational leaders develop their professional identity. Our objectives were: (a) to identify the factors that determine how educational leaders develop their professional identity; (b) to identify shared traits of educational leadership identity; and (c) to describe the implications that the results obtained may have for research and professional practice. A literature search on Web of Science (WOS), SCOPUS and Education Resources Information Center (ERIC) yielded a total of 38 articles published in international journals. Thematic analysis was conducted using the Nvivo software package. Emerging topics include: leadership identity of school principals as the key to educational success; influence of politics and context on the construction of principals' professional identity; race- and gender-based barriers to the development of leadership identity; and the influence of experience, training and transition on the construction of a professional leadership identity.