In this study, the opinions of middle school science teachers and mathematics teachers towards STEM education were examined. The research was carried out for 30 hours with 28 middle school science and mathematics teachers who were working in Istanbul during the spring semester of 2016-2017 academic year. 75% of these teachers are female teachers and 25% are male teachers. The study was conducted by the case study method among qualitative research methods. For the determination of the opinions of the secondary school science and mathematics teachers by the researcher, "STEM Interview Form for Teachers" consisting of 8 questions was created. As a result of the analysis, the teachers emphasized that they did not feel sufficient about STEM education. In addition, teachers emphasized that a good STEM teacher should have STEM knowledge, pedagogy knowledge and 21st century skill knowledge. However, they emphasize that STEM education is a useful educational concept but that there may be problems that may be encountered during STEM education. Moreover, it was also found that after the STEM training, teachers had positive changes in their opinions towards Engineering and Technology. Suggestions have been made in the direction of these obtained results.