The main purpose of this study was to explore grade eleven EFL teachers’ perception and implementation of cooperative learning in EFL classes of Dembecha comprehensive and secondary school. To put this into effect descriptive design was used. To collect data six grade eleven EFL teachers were selected through comprehensive sampling method and seventy two grade eleven students were selected through stratified random sampling method. In addition, the school supervisor who was selected through purposive sampling method used as a source of data. After the data had been collected through questionnaire, interview and classroom observation, the analysis was done both quantitatively and qualitatively. That is, almost all of the data obtained by questionnaire items were analyzed quantitatively using frequency, percentage and mean and the data obtained by classroom observation was analyzed using frequency and percentage. The rest data obtained through the open ended item of EFL teachers’ awareness of CL and interview were analyzed qualitatively alongside the quantitative data After the data analysis, the results indicate that EFL teachers’ perception of CL was low, that is, they did not clearly know what CL is (definition, essential elements, roles of teachers and students, etc) as a result they did not implement CL well that the implementation was low, however, the classroom condition; seats were suitable and number of students was manageable to implement cooperative learning. Finally, based on the above findings, some recommendations have been forwarded that grade eleven EFL teachers should get cooperative learning training theoretically and practically and also the school should supply supplementary materials that help teachers to have adequate perception of cooperative learning and implement it in EFL classes.