This article describes outcomes from the Erasmus + project botSTEM, involving a theoretical framework for Science, Technology, Engineering & Technology (STEM) and robotics and teaching activities for preschool teachers and teachers educating children 4-8 years old. Spanish and Swedish preschool teachers' self-efficacy and views of teaching STEM and robotics are presented, using a mixed methodology based on a questionnaire and focus group interviews. The 3-year long project has improved the preschool teachers' self-efficacy in STEM and robotics teaching, as described in a questionnaire answered by the preschool teachers after the project. Possibilities in STEM and robotics teaching experienced by them include an increase in children's agency, knowledge and interest, and the obstacles are mainly structural or technical. Robotics teaching also supports children with special needs when interacting with peers. The results from the botSTEM project point to the benefit of supported long-term professional development for STEM and robotics teaching in preschools.