The aims of this study are to reveal how science teachers integrate science, technology, engineering and mathematics (STEM) in their lessons and their opinions regarding the advantages and disadvantages they have identified while integrating STEM in their lessons, as well as what kind of difficulties they encounter in the implementation process. For this purpose, a semi-structured interview form was developed and qualitative research method was used. STEM is based on a holistic and interdisciplinary approach to the four disciplines rather than the independent teaching of these four disciplines. The study group comprises 12 science teachers in the province of Mugla in the 2017-2018 academic year. Research findings show that science teachers generally have a positive attitude towards using STEM-based activities but are not able to implement STEM-based activities in an appropriate, complete and accurate way because of difficulties in terms of 'physical conditions' and 'time management'. Teachers stated that STEM education encourages students to do research.