Preschool science, technology, engineering, and math (STEM) is important for later learning for all children, including dual language learners (DLLs). However the preschool workforce is generally not well prepared to teach STEM or to work with DLLs, and attitudes and beliefs may play a role in teachers feeling challenged to provide high quality STEM teaching. The objectives of the SciMath-DLL professional development (PD) model are to improve attitudes and change beliefs of educators, increase preschool teachers’ knowledge, and improve classroom instruction around STEM and supports for dual language learners (DLLs). This paper provides preliminary results from a randomized trial of participation in the SciMath-DLL PD on preschool educators’ attitudes and beliefs.