STEM (Science, Technology, Engineering and Mathematics) approach is considered important by many countries and projects carried out in order to integrate into their curriculum. The widespread use of STEM is only possible if teachers have positive thoughts, knowledge and experiences about it. In this study, it is aimed to answer these research questions: "What do teachers think about the gains their students will achieve if STEM activities are implemented to their students?" and "What do they think about the implementation of STEM approach in their schools?". This study is a case study. Participants are twenty-three mathematics, science and information and communication technologies teachers (ICT). "Activities Evaluation Form" and "STEM Training In-School Implementation Evaluation Questionnaire" were used as data collection tools. As a result of research, although teachers have hesitations about implementing STEM activities in classrooms; they think that these implementations will make a significant contribution to students about the "skills" students will acquire, the dimension of knowledge they will gain about STEM activities, and the acquisitions of students regarding the learning process.