The purpose of this study is to investigate the effects of using mobile-based vocabulary game activities on Korean middle school students' vocabulary learning and attitudes. The participants of the study were 43 middle school students learning English, who were divided into two groups: an experimental group with learning activities using a mobile-based vocabulary game program and a control group using traditional vocabulary learning activities. The major results of the study were as follows: First, with respect to vocabulary learning, the students in the experimental group showed a significantly higher score on a post-test compared to the control group students. Second, the experimental group’s scores were higher than the control group in both vocabulary pronunciation and spelling tests listening to the pronunciation. Third, in the survey the participants demonstrated positive attitudes toward vocabulary learning using the mobile-based vocabulary game program. Such results indicate that the use of a mobile-based game vocabulary program helps learners to learn not only the spelling of vocabulary and its single meaning but also the multilateral vocabulary learning such as listening and pronunciation. Therefore, teachers may use learner's mobile-based vocabulary game programs to inspire students’ interest in vocabulary learning, and encourage self-directed vocabulary learning.