There are many different perceptions when it comes to teachers’ instructional language choice in the EFL classroom. Some argue for maximum use of the target language while others believe that judicious use of the L1 can benefit the students’ second language learning. The aim of this study is to investigate what research says about teachers’ target language use and first language use in upper level EFL classrooms, as well as teachers’ attitudes and beliefs regarding the choice of instructional language. The findings from this systematic literature review show that teachers mainly used L1 to save time, to explain grammar and vocabulary and to create a positive classroom atmosphere. Furthermore, the results also showed that teachers’ choice to use L1 heavily depended on students’ level of proficiency. Lastly, the results indicate that teachers not always use the L1 for pedagogical reasons, but in many cases for pragmatical reasons, individual beliefs and out of concern for students’ well-being.