This study aimed at investigating where and the purposes for which code-switching is used by Iranian EFL lecturers in universities as foreign languageinstruction.The data of this study were gathered from two sources: six EFL university lecturers from three local universities where they taught English as EFL instruction.Theywere interviewed individually regarding the use of code-switching in their classrooms in order to reveal their purposes of using this strategy as well as their participants' understandings of code-switching as a language teaching strategy. The interviews took 30-40 minutes each. The interviews were finally transcribed and the main themes were coded to answer the research questions; the second group of participants was students as native speakers of Persian. Ninety undergraduates from the three universities were randomly chosen from among those students majoring in TEFL. They were majoring in the first grade of the academic program. To this end, an eleven-item questionnaire was given to them to elicit their responses for the contexts and the reasons for which code-switching was preferred.The data from interview with EFL lecturers as well ISSN 2162-6952 2016 www.macrothink.org/jse 96 those of the students' responses were analyzed qualitatively and quantitatively using SPSS, respectively, to determine where and for what purposes codes-switching were applied or practiced in EFL classrooms. The findings of the study indicated that their code-switching habits were connected to what was being taught. Their code-switching had to do with efficiency in their teaching and how to make it easier for the students to understand what they were teaching. Journal of Studies in Education