this study investigated the functions, types and frequencies of code switching in the teachers and students discourse in elt classrooms. to this end, the participants of this study including two groups of teachers and students were selected. the first group of participants were two efl teachers teaching general english courses (at two different levels of proficiency) in an institutional program in oil ministry center of isfahan. another group of participants were 20 students in two classes. all sessions of an entire semester was videotaped. a coding scheme was developed for classifying teachers’ and students’ instances of cs into relevant functions. the current study shows that the majority of cs in the classroom is highly purposeful, and related to pedagogical goals. also, the research found that pedagogical functions were more frequently fulfilled through cs compared to social functions both for teachers and students. the present study can help teachers to have a better understanding of teacher and student code switching in elt classrooms and to use cs in the direction of teaching and effective learning.