Essay writing is considered a significant skill at graduation level in Pakistan. However, it is taught in traditional teacher-centered ways in most of the colleges and universities where students do not get a chance to collaborate and interact with other class fellows. Kagan (1992) has suggested the use of cooperative learning in teaching writing to students. This research was carried out to find the impact of cooperative learning on students’ essay writing skills at graduation level in a public sector university in Pakistan. The main objective of the current study was to determine whether cooperative learning could be used as an effective method for teaching essay writing skills at graduation level in Pakistan. In this regard, an experiment was conducted to see the impact. Experimental group was given a treatment in the form of cooperative learning technique whereas control group was taught as usual. The instruments used in the present study were pretest and posttest. The data collected through pretest and posttest were analyzed through descriptive and inferential statistics. The students’ writing performance was assessed employing the writing evaluation rubric in Ismail’s (2006). The five writing components, content, vocabulary, organization, grammar, and mechanics were analyzed. Findings of the study suggested that the overall performance of the experimental group was significantly better than that of the control group on posttest. This study proved that there was a positive impact of cooperative learning on students’ essay writing skills and that cooperative learning could be used as an effective technique to teach essay writing skills at graduation level.