Early STEM education has a great potential to support children’s development in constructing their own knowledge, in designing, discussing and testing ideas and finding solutions to different problems. Significant role in achieving the goals of STEM education is played by the teacher, who scaffolds the learning process, builds a creative learning environment, provokes children with open questions and guides them to test their hypothesis as young scientists, mathematicians, engineers and technology users. Preschool teachers’ knowledge and perspectives could seriously influence their practices in STEM education and respectively, the fulfilment of STEM learning outcomes. It is very important to explore in depth teachers’ views and experiences thus to plan and provide appropriate courses for their academic preparation or continuous professional development. While reviewing some popular misconceptions for STEM education amongst teachers, this paper presents the results of pre- and post-interviews conducted with teachers from Bulgaria in the framework of the European multilateral Erasmus+ project №2018-1-TR01-KA203-059568 “STEM for Pre-schoolers and Their Families” (PARENTSTEM) (2018–2021). The overall goal of this project was to increase family involvement in the STEM education process of early childhood children specifically coming from low socio-economic status. As a part of this goal implementation, the project aimed to extend conceptual and pedagogical knowledge of early childhood teachers on STEM. In the frame of the project the preschool teachers-participants in the study were provided with three teacher trainings (two international and one national) and were additionally supported with the intellectual outputs of the project. This paper attempted to identify teachers’ preliminary knowledge, awareness and attitudes towards STEM conceptualization and pedagogy and to describe the relative influence of the project teacher trainings and activities on them. The results of the research unambiguously demonstrated the need for training of preschool teachers in terms of STEM education, outlining the main focuses to be considered when constructing STEM courses intended for preschool teachers.