This research was conducted to investigate the improvement of using flashcards in teaching vocabulary to fifth graders of MI Miftahul Huda Batealit Jepara. The subjects of this research are the fifth graders. The researcher uses a classroom action research as a method in conducting this research. Based on the findings of the research, students’ vocabulary mastery improved after they were taught by using flashcards. They could memorize the words easily, be more motivated to learn English and understand vocabulary easily. The result shows that flashcard is able to help students to improve their vocabulary mastery. There is improvement from cycle 1 to cycle 3; it can be seen from the result of every test. In the first test, the average score of the class is 76, 4. Then, in the next test is 78, 2. The average score in the last test is 79, 5. It can be concluded that by using flashcards, students can improve their English vocabulary mastery. The result also showed that flashcards could lead the students to a higher level of vocabulary improvement. It was concluded that using flashcards is recommended to teach vocabulary to young learners.