The aim of this research is to know whether using fly swatter game can improve students’ vocabulary mastery at the seventh grade of MTs Darul Ulum Purwogondo Kalinyamatan Jepara in the Academic Year of 2020/2021. This research was quasi experimental research as the design of the research. The population of this research were the seventh grade students of MTs Darul Ulum Purwogondo which consisted of 316 students. The sample of this research was 2 classes, they were class H consisted of 32 students as experimental class and class E consisted of 32 students as control class. Totally was 64 students as the sample. The sample was taken by using purposive sampling. The instruments of this research was vocabulary test consisted of 20 questions multiple choices. The data from pre-test and post-test were analyzed statistically using spss 25. The finding of this research was the students’ pre-test mean score was 45.93 in class H and students’ mean score was 43,28 in class E. The students’ post-test mean score was 72,34 in class H and the students’ post test score was 64,53 in class E. The result of t-test was 0,001. It was showed that Sig. (2-tailed) was lower than 0.05 (0,001 < 0,05). It was indicated that there is significant between experimental class and control class in post test score. The Null Hypothesis (Ho) was rejected and the Alternative Hypothesis (Ha) was accepted. Based on the findings and the discussion of the research, the researcher got a conclusion that the use of fly swatter game was effective to improve students’ vocabulary mastery at the seventh grade students of MTs Darul Ulum Purwogondo Kalinyamatan Jepara in Academic Year 2020/2021.