This study was conducted to analyze the effect of message frame on Exercise Interest and User Experience including Fitness App Fun, Fitness App Satisfaction, and Fitness App Use Intention in the mobile fitness app game. ‘Enjoy Your Fitness’, a fitness app game developed by Healthcare Media Research Institute, was used for this study and Repeated Measure Design and Playtest methodologies were used for the experiment. The results showed that the persuasive effect of gain messages were higher than loss messages in all factors. This results implies that exercise, as a preventive health behavior, can be promoted more effectively when messages are presented in the frame of gain message rather than loss message. Therefore, messages in the fitness app game need to be presented by emphasizing the positive outcome and benefit of exercise.