ABSTRACT Siti Khasinah, 2015. The Use of Student Teams-Achievement Divisions in Improving English Grammar of EFL Learners (An Experimental Study at the State Islamic University Ar-Raniry). Thesis, Graduate Program in English Language Education Syiah Kuala University. Advisors: (1) Dr. Sofyan A. Gani, M.A, (2) Dr. Zulfadli A. Aziz, S.Pd., M.A Keywords: Cooperative Learning, Students Teams-Achievement Divisions (STAD), grammar ability. The present study aims at finding out whether the use of Student Teams-Achievement Divisions improves students’ achievement in grammar. It also aims at finding out if teams’ scores reach award criteria proposed by Slavin (1991) after the use of Student Teams-Achievement Divisions. In the experimental class, cooperative learning STAD was used to teach Grammar Three Course. In control class, the mean of pretest was 58 and the mean of posttest was 65 with gain score 7. Meanwhile, the mean of pretest in experimental class was 54 and the mean of posttest was 65 with gain score 11. Additionally, from t-test, it was found that to was 1.89 with ttable 1.67. It can be said that the score of to was higher than the ttable in level of 5% where 1.89 > 1.67. This meant that the alternative hypothesis which stated that the students of English Education Department of the State Islamic University Ar-Raniry get better achievement in grammar after being taught by using Student Teams-Achievement Divisions than those who are taught by not using STAD was accepted and the null hypothesis was rejected. From the result of group scores, it can be said that the total average of improvement points from all groups were 21. Therefore, the award criteria gained was Great Team or level 2, referred to the award criteria proposed by Slavin (1990).