The use of developmental bibliotherapy has been acknowledged as an effective strategy of promoting social and emotional development, personal and educational benefits of children. The goal of this paper was to estimate the self-assesement competences of educators in regards to using developmental bibliotherapy in their educational work. 259 educators of children of early and pre-school age took part in this research. The results show that the competences of using the developmental bibliotherapy are gained only to a small extent during the initial education, and to moderate extent during the long-term professional development. Educators have self-assessed their competences of using different type of literature as moderate, whereas their competences for choosing literature, implementing it, using stories for social inclusion, monitoring social-emotional development and adjusting stories to individual needs of children were estimated as acquired to a larger extent. Higher chronological age and years of work experience are in correlation with assessing a higher level of gained competences for using the developmental bibliotherapy during the long-term professional development, whereas younger educators with less years of work experience, assessed to have gained a higher level of competences during the initial education. The level of education as well as the way the preschool educators perceive the availability of professional support play a crucial role for the perception of their own competences in applying developmental bibliotherapy. In conclusion, it is important to promote both formal and informal education of preschool teachers as a basis for applying developmental bibliotherapy in their educational work, with the goal of promoting the children's well-being. In addition, it is important to secure and promote the availability of professional support.