The aim of this study is to find out whether crossword puzzle game is improved students’ vocabulary mastery. This research was a quantitative research using quasi-experimental as the method in collecting data in two classes, an experimental and a control class. In this study the data was taken from pre-test and post-test. The SPSS program was used to analyze the normality, homogeneity, hypothesis and t-test. The students’ scores of experimental classes were higher than the students’ scores of control class. The result shows that the mean of pre-test from experimental group was 55,63, and control group was 48,54. Then the mean of post-test from experimental group was 79,68, and the mean of the control group was 67,92. There was significant difference between the students’ achievement who were taught by using crossword puzzle game and those were taught by conventional method. The T-test revealed that the result was determined by p<0.05, p=0,000. Thus, H1 was accepted. This research concluded that the Crossword Puzzle game is effective to improve students’ vocabulary mastery in SMPN 2 Kuala, Nagan Raya.