Teachers must use appropriate games to improve student's English vocabulary and speaking skills based on their prior knowledge, and the Monopoly game is ideal for developing students' vocabulary achievements. This research goal is to determine the effectiveness of Monopoly games in improving students' vocabulary and speaking skills. The researchers used a mixed method. Researchers collected quantitative data from classroom action research (CAR) in the tenth grade DKV A of SMK Ma'arif 1 Kebumen using purposive sampling of about 30 students, and the results of the analysis were qualitative. From October to November 2022, research was conducted. The collecting data used were observation and tests. The results of the study use percentages and averages in analyzing data. The results of the analysis are as follows: (1) the implementation of the Monopoly game in vocabulary mastery motivates students to increase their vocabulary and speak English, (2) the observations show that students enjoy playing Monopoly games while learning vocabulary, and (3) the test results show that all students have passed the test and improved their skills in speaking English. It can be concluded that the use of Monopoly games can support improving vocabulary mastery and developing speaking skills.