The aim of this dissertation was explore the beliefs and practices of pre-service primary teachers on using simulations as a part of guided inquiry-based lessons. Even though research has shown that using simulations to learn science offers certain learning benefits compared to other forms of instruction, their use in Finnish schools is still rare compared to the international average. Teacher training has the potential to promote the use of simulations in primary classrooms. Internationally, research has been called for the role of teachers in learning and teaching with simulations. As a part of this dissertation, an intervention was designed to accustom a group of pre-service teachers to teaching science with simulations. As teacher beliefs play a critical role in the implementation of new technologies into classrooms, the connection of pre- service teachers’ beliefs about their knowledge in different domains to their attitudes towards simulations was examined. The focus was also on how the pre-service teachers provided guidance for inquiry-based learning with simulations in the lessons that were a part of the intervention. The findings show that the pre-service teachers’ belief on their own technological knowledge correlates with their attitude towards simulations. As for providing guidance for inquiry-based learning with simulations, the findings demonstrate the important role teachers have on providing guidance that adapts to both the simulation and to the students’ needs. The forms of guidance had also an effect on the communicative approach the pre-service teachers applied in the lessons. The results provide insight on the unique role of the teacher in science teaching with simulations but as well give guidelines to teacher educators on how to promote high quality inquiry-based science teaching with simulations through teacher training. These guidelines include improving the technological knowledge of pre-service teachers throughout their teacher training and ensuring that they are able to recognize the potential different providers of guidance have on supporting inquiry-based learning.