During the last twenty years significant changes have taken place in the field of inclusion of children with developmental disabilities in mainstream kindergartens in Croatia. According to the legal regulations of the Republic of Croatia, children with developmental disabilities have the right of priority when enrolling in kindergartens. Nevertheless, in practice, certain shortcomings and challenges can be observed - that can impair the quality of inclusion if there is no timely intervention – such as insufficient additional support for preschool teachers in the implementation of inclusive preschool education. The aim of this study was to verify the process and the impact of implemented educational modules for preschool teachers and inclusion/educational assistants. The modules were developed as part of the IPA project “Supporting inclusion of preschool children with developmental disabilities in mainstream kindergartens in Croatia“, which was co-financed by the European Social Fund. The study was conducted on a convenience sample of workshop facilitators (N=5) from Zagreb and Split, alongside inclusion assistants and preschool teachers from partner and collaborative kindergartens from Zagreb, Split, Zadar and Karlovac (N=122). The workshop facilitators individually filled out a suitable constructed satisfaction questionnaire on the implementation and results of the project (process evaluation), and all participants have filled out an appropriate anonymous questionnaire – either for preschool teachers or for inclusion assistant. The group questionnaires were conducted at two time points – before and after the project implementation. The level of overall satisfaction of the workshop facilitators was higher at the end of the project implementation, compared to the start of the project, whereas the highlighted challenges were related to the lack of experience in designing and conducting workshops. Furthermore, after the educational modules were delivered, the level of knowledge of teachers and assistants was significantly higher, and the attitudes about the inclusion of children with developmental disabilities in mainstream kindergartens were significantly more positive. In order for the results to be generalizable, further checks with a more heterogeneous sample of participants, as well as delayed application of the questionnaire, are necessary.