This Classroom Action Research is conducted to improve students\u27 vocabulary mastery through Jumbled Letters Game.. Field notes were also used to monitor the teacher and students\u27 performance. The result of data analysis showed that class VIIA students got their progress in mastering vocabulary. In the first cycle, the students\u27 mean score of vocabulary mastery was only 58.57 and categorized as poor. By doing all the steps of classroom action research, the process of teaching and learning was evaluated and modified, including providing clues for the students during playing the game. Then in the second cycle, the mean score of the students was improved to 72 which categorized as good. It showed that there was an improvement of the students\u27 English vocabulary mastery after applying the jumbled letters game during teaching learning activity
