This study is aimed to find outthe effectiveness of using Gametolearnenglish to improve students’ vocabulary mastery of the fourth graders of SD IT Muhammadiyah 04, Truko in the academic year of 2016/2017.This study was conducted at SD IT Muhammadiyah, Trukowhich is located on Jl. RayaSoekarno – Hata Km 10,Kangkung,Truko, Central Java, Indonesia. The type of this study was quasi experimental design.
The population of this study was the fourth graders of SD IT Muhammadiyah, Trukoand the sample were IVC class as the experimental group and IV Aclass as the control group. In collecting the data, the researcher used test named pre-test and post-test.The result of this study showed that the pretest mean score of experimental class was 65.00 and that of the control class was 61.50. After giving treatment for fourth meetings, the post-test mean of experimental class was 79.50 and that of the control class was 69.50.The result of the analysis showed that there was a significant difference. It was supported by the result of t-test that showed sig (2-tailed) was 0.004. It could be concluded that H0 was rejected and H1 was accepted and that it is effective to improve students’ vocabulary mastery. Therefore, the use of Gametolearnenglishwas effective to improve students’ vocabulary mastery.

Keywords: Gametolearnenglish,Vocabulary Mastery