Abstract: Reading comprehension is a major component of language learning and finding an appropriate and effective way for teaching it, was considered by many researchers. However, one effective way for achieving this goal can be using different activities. The purpose of the researcher is to show the effectiveness of cooperative learning, more specifically jigsaw task on reading ability of Iranian intermediate high school EFL learners. In order to check general language proficiency of the students, 120 female students were randomly selected and Nelson Proficiency Test was given to these students. Sixty students were selected from among 120 female students and they were assigned in two different classes. After selecting 60 students, they were divided in two groups, one of them as the experimental group ( G1) , and the other as the control group ( G2). Each group consisted of 30 students. Their ages ranged from fifteen to nineteen. First session both groups received pretest. After that the experimental group received treatment in jigsaw task during six sessions and control group received traditional method. Last session both groups received posttest in order to check reading ability. Statistical results revealed that the experimental group did much better than control group and consequently jigsaw task was effective on reading ability of Iranian intermediate high school EFL learners.