The aims of this study was to evaluate the effectiveness of using Word Square media in improving English vocabulary mastery. This study used an experimental research design with data collection techniques using tests, documentation, and hypothesis testing, with samples taken from class X TKR 2 as the experimental class and X TKR 3 as the control class. The results of this study showed that the learning outcomes of the experimental group effectively increased. In addition, from t-test, the sig.2 tailed value of 0.000 indicates that there were differences between acquiring vocabulary with and without Word Square as a medium because the significance level was below 0.05. Ha was approved where as H0 was denied. This indicated that there was a significant difference in the vocabulary knowledge of the first graders at SMK Wiratama 45.2 Wonosobo between those who were taught without and those who were taught using Word Square as media.