In this article, we present the evaluation of a kindergarten teachers' professional development programme, 'Upgrading the quality of the pre-school environment' conducted by the participating teacher--thee programme is aimed at the improvement of the quality of Early Childhood Education and Care. The evaluation, which followed a mixed-method design, combining quantitative and qualitative approaches, was based on Guskey's (2002) five levels model. ?he Interconnected Model of Teacher Professional Growth (Clarke, D., & Hollingsworth, H., 2002) was used to study participants' professional growth. Fourteen teachers serving in public Kindergartens in Greece participated in this study (n=14). Findings showed that the overall programme, the acquisition of knowledge and competences and the possibility of their application in the teaching practice were assessed as positive. The significance of a supportive context in the application of new knowledge and practices was also outlined. Moreover, the main correlations between domains of the Interconnected Model of Teacher Professional Growth are presented, which depict the sequences through which the changes in the teachers occurred. Therefore the present research provides valuable information regarding the design of future professional development programmes aiming to improve the quality of the preschool environment.