This research is aimed to describe and analyze the students? mastery in English vocabulary before and after applying the teams games tournament using word square. Also, to analyze the influencing factors that increase students? vocabulary mastery. The samples of this research are 22 students of class 7 from SMP Frater Don Bosco Tomohon. The research is an experimental study with a descriptive quantitative and qualitative approach used quasi-experimental, pretest and posttest one-group design. The methods used in collecting the data are interview, observation, questionnaire, and test. To analyze the data, quantitative and qualitative methods are used accordingly. The theories used in this research are teams games tournament theory, constructivism theory, and vocabulary learning theory. The result of this research showed that after applying teams games tournament using word square, the students? mastery in English vocabulary are increased. There are 20 students have fulfilled the standard completeness score while only 2 students who have not. The class average score reached 82.81 (good). Based on the paired sample t-test conducted, it is known that the tcount value is greater than the ttable which is 9.388 > 2.079. Thus, it can be concluded that there is an effect of applying the teams games tournament using word square towards English vocabulary learning.