Purpose: The purpose of this paper is to propose an emerging approach in research on school leadership, within the framework of the "International Successful School Principalship Project (ISSPP)", where one of the three key research strands is "Principals' identities". Design/methodology/approach: The paper responds, from a biographical-narrative approach, to knowledge about the impact of the Spanish model of school management on the professional identity of school principals. It analyses the biographical interviews of 15 school principals, through a process of structuring and categorizing the data collected, applying content analysis. Findings: The dimensions of the principals' identities emerge in different categories: personal identity, professional identity (internal perspective), professional identity (external perspective), social identity, professionalization and dual identity. Research limitations/implications The authors studied identities in a project entitled "Successful school principals", understanding that successful leadership practices largely depend on headteachers' identities. That is, when the identities are weak and unstable, with a poor identification with the managerial tasks and functions, and not recognised by the teaching staff, the school will probably be unsuccessful. On the contrary, when there are headteachers with a strong professional identity, the authors want to show that there is a positive impact on improvement of results. In the future, in the development of the research project, the authors aim to verify the relationship between headteachers' identities and educational improvement. Practical implications: The knowledge gained in our study would enable us to reimagine lines in order to increase the professionalization and identities of headteachers, redesigning work contexts in ways which can strengthen fragile and unstable identities. Finally, the implications of the study in relation to future research can be summarised by the following ideas. Social implications: Understanding the world of the lives (lebenswelt) of Spanish headteachers means adopting a hermeneutic approach, observing the self-interpretation comments expressed by the subjects, where the temporal and biographical dimensions occupy a key role. The authors understand professional identity as a socially constructed and personally created experience with its own meanings, feelings and intentions. Therefore, it is logical to use, for data collection, individual interviews which explore the school context and the impact which it has on those subjects who are part of the professional environment. In addition, the authors have the intention of following up the study of identities. Originality/value: It formulates, first, the theoretical framework for the professional identity from a narrative approach, linked -- at the same time -- to the practice of leadership, as an interactive relationship with the other members of the school. Successful leadership practices depend to a large degree on strong principals' identities. Finally, the results are discussed, and future lines are proposed to articulate and strengthen the identity of school principals in Spain.