Abstract: With the huge advance of technology, teachers can utilize different online applications in teaching and Quizziz is considered as one of the applications commonly used to create online quizzes in teaching and learning activities. This study was conducted with an aim at investigating the effectiveness of using Quizziz on improving students’ medical vocabulary achievement after four weeks learning medical English. Accordingly, this study was conducted as action research followed some steps including planning, acting, observing and reflecting with forty students at Thainguyen University of Medicine and Pharmacy (TUMP) participating in the study.