Vocabulary is a linguistics ellement of language skills. The purpose of this research is to describe the role of BBC’s Video in Instagram for improving students’ mastery on vocabulary. This research is a class room action research based on the theory of Kemmis and McTaggart (1988). The researcher used three times of classroom action cycle to achieve the goal. The population of this research is students at SMP Negeri 3 Medan and the sample is students at grade seven-two. The data of this classroom action research is score from each cycle. The result of this research shows us that BBC’s Video in instagram as a media of teaching English is able to improve students’ mastery on vocabulary. It can be seen in the first cycle their average score is 60.1, in the second cycle is 72.3 and the last cycle is 85.1. This result shows us that video in instagram is a good instrument to improve the students’ mastery in vocabulary. It is suggested to other English teacher to make this media as an alternative media as far as the teaching method is supported to use.