The aim of this research is to interpret and discuss the findings of qualitative research that has put forward the teachers' opinions, code switching and using L1 (First lanaguage) through a systematic research method in education called "meta-synthesis." As a result of this meta-synthesis research (N = 18), the teachers stated that they generally viewed the use of L1 and code switching in the classrooms positively. Academic, managerial, social or cultural factors and pedagogical purposes themes were reached as the cause of using L1 in the classes. Moreover, subthemes were to teach difficult grammar, to practice vocabulary and enhance pronunciation, to check comprehension, to give instruction, to maintain discipline, to save time, to make students feel comfortable (decreasing student stress and anxiety), and connected to their teacher, to motivate, to maintain interaction, making students not having enough proficiency to understand, to talk about feelings, emotions, culture, experience (pedagogical matters), etc. In addition, teachers also drew attention to the controlled use of L1 or code switching in the classroom. On the other hand, some teachers did not find the use of L1 or code switching appropriate, and the themes related to these were to create an authentic learning environment and to capture attention.