This study investigated the effects of Cooperative learning on students’ writing performance. The general objective of the study was to investigate the effect of cooperative learning on students writing performance in EFL on grade 11 students at Hageregenet secondary and preparatory school. The research design was a quasi – experimental design. Both qualitative and quantitative data collection methods were used to gather valuable data. From all six sections of grade 11 students, two sections were selected by using the intact, existing group as sample based on their approximately equivalent mean value of the pre test result. Later, the selected sections were randomly assigned in 2 groups of the experimental and the controlled. The experimental group was thought through cooperative learning methods while, the control group was taught by the old method which is teacher centered. A posttest was administered after ten weeks intervention by using similar text. Then after, an interview was employed to the experimental group so as to know their outlook towards the newly applied teaching strategy in their EFL classes. Finally, the results were analyzed through an independent and paired t-test as well as thematically. The findings of the study show that Cooperative learning methods were more effective in enhancing EFL learners writing performance