The idea behind this work sprung from the need to deepen the understanding of the preschool head teacher’s professional work and point to the significance of possessing professional competences for successful governance. Since research on this topic is not abundant in the field of early and preschool education in the Republic of Croatia, the content of this work will enrich the literature and provide a more in-depth portrayal and understanding of the stated issue. Managing a preschool institution is considered a complex social and pedagogic phenomenon which requires much more than simply working as the Head. In order for this governance to be attributed with the characteristics of successful guidance, head teachers need certain competences and qualifications. In the theoretical part, through seven chapters, this work focuses on professional competences and professionalization of the head teachers and it examines this process in the Republic of Croatia. In accordance, the work continues with the review of the profession's standard in certain countries, which successfully regulated the head teacher’s position into a profession; and the proposition for the occupation’s standard, qualifications and licencing models, resulting from the efforts of the expert work-group appointed by the Ministry of Science and Education in 2015. In order to assess the professional role of head teachers, attention needs to be directed to some factors within the area of the institution's high-quality work, especially human relationships, which is presented in the empirical part of this work. It is of importance to point out that the organisational management of a preschool institution relates to the head teacher, but also to preschool teachers, expert associates and other concerned parties within the institution. The thriving of cooperative relationships climate depends in great measure on the head teacher's professional competences, his/her knowledge, skills, experience and motivation. Team work and supportive relationships within the institution is the key to successful professional growth and development of the institution and its workers; the head teacher, as a motivator and promoter of such atmosphere, is considered a relevant factor. The empirical part of the work utilises the Self-assessment Questionnaire measuring attitudes of the employees about the key to the preschool’s work quality and their satisfaction with it, as follows: the Questionnaire for the head teacher, the Questionnaire for the preschool teachers, the Questionnaire for the members of the expert team, the Questionnaire about the head teacher's behaviour, the Questionnaire about the assessment of the relationships in preschool institutions and the Scale of the head teacher’s self-assessment of competence. The research was implemented with the use of the survey method in preschool institutions (N=57) in the area of Central Croatia – the counties of Varaždin, Karlovac, SisakMoslavina and Zagreb, and the city of Zagreb, in June and July 2020. The head teachers were previously approached with the request for the research implementation, informative form with the stated goal and purpose of the research, and in such a way their consent was obtained. In the empirical part, five hypotheses were set, out of which three were confirmed (one partially), while one was not confirmed. For testing the hypotheses, univariant and multivariant quantitative approach was used, which included descriptive and inferential statistics, parametric, nonparametric and robust tests, bootstraping of the values, bayesian assessments of the statistical parameters and distributions (loglikelihood, prior and posterior). The significance of the preschool Heads’ professional competences for the development of the institution's work quality was confirmed by the research results. Furthermore, the assumption was confirmed that head teachers who assess themselves as professionally competent perceive their behaviours and relationships more positively, which effects greater quality of the preschool’s work, thus achieving the research goal. The conclusions derived from this work indicate the necessary (re)definition of the head teacher's role, regulating the position into a profession, and systemic and continuous provision of his/her professional development. Professionally competent head teacher is the key to success in developing the work quality of a preschool institution, because he/she has the possibility and capability of positively shaping and influencing its entire functioning. Theoretic considerations contribute to better understanding of the preschool Head’s professional activity as a complex phenomenon which requires professional approach in all areas of his/her work. Conclusive considerations of the work point to its possible contribution, but also drawbacks and limitations.