In the primary school level, English is no longer a compulsory subject to be taught. In some schools, English is only a local subject. As a result, when students enter secondary school, they have very little knowledge of the English language. This is also the case in SMP 1 Kabat. Students' knowledge of English vocabulary is very low. Therefore, teaching vocabulary becomes crucial because vocabulary mastery is the foundation of learning the other four English language competencies. This research aims to enhance the participation and vocabulary mastery of 7th-grade students at SMP 1 Kabat using Flashcards as a media. This study employs the Class Action Research (CAR) method, consisting of two cycles, each with four stages: planning, acting, observing, and reflecting. Collaborative action research (CAR) is conducted, meaning students work together with the English teacher. The researcher collects data using tests, observations, and questionnaires. To analyze the data, the researcher uses both quantitative and qualitative descriptive analysis. Based on the research conducted, it was found that the percentage of student participation in the learning process in cycles 1 and 2 was 76.67% and 86.67%, respectively. As for the learning outcomes in the first cycle, it was 57%, which did not meet the passing target. However, in the second cycle, there was an increase to 80%, surpassing the minimum target of ≥75%. Based on the results obtained from the research, it can be concluded that the use of Flashcards as a media is highly effective in improving the participation and vocabulary mastery of 7th-grade students at SMP 1 Kabat.