This study has the purpose to investigate the implementation of Taboo game to improve students’ vocabulary mastery. The method used in this research is classroom action research. The research was conducted in two cycles at SMP Negeri 1 Semin Gunungkidul started from 13^th February 2020 to 27^th February 2020.  The participants were 32 students of VIII A of SMP Negeri 1 Semin Gunungkidul. Each cycle consisted of four stages: planning, acting, observing, and reflecting. This research used several data instruments, i.e. observation checklists, tests, questionnaires, and interviews. The research findings showed that Taboo game can improve students’ vocabulary mastery. The mean score of the students in the pre-test increased significantly from 56.07 to 97.3 in the second post-test.