The purpose of this study was to construct a prevention model for adolescents' game overindulgence and to test the validity of the model. Two research questions set up for the study were the followings: 1) What are main domains and their content factors of the prevention model for adolescents' game overindulgence, which is based on literature on game overindulgence, an analysis of existing programs and in-depth interviews with specialists in consultation for adolescents. 2) Is the prevention model for adolescents' game overindulgence valid? For the first research question to be answered, firstly, previous studies analyzed the concept of adolescents' game overindulgence and the related variables, and designed a draft of a program model based on in-depth interviews by counseling specialists for adolescents. For the second one to be answered, delphi was conducted twice in order to verify the content validity of the draft. Delphi verification for the content validity was rated by using 5.0 Likert scale in terms of representativeness, clarity, and comprehensiveness. The model was revised after analyzing the mean scores of each item, the content validity ratio(CVR) and opinions suggested by delphi panel. Reflecting numerical results of the first delphi performed and opinions from experts, a questionnaire for the second delphi was constructed and then conducted. According to the second delphi survey, the degree of consensus among panel of experts was relatively high in that the average is more than 4.5 and the content validity ratio is 1.00. As a result, the finalized prevention model of game overindulgence consists of a total of 15 categories, 45 sub-divisions and 48 details. It is as follows: 1. the process of game overindulgence, 2. the environmental factor of adolescents overindulged in games, 3. the characteristic of counseling for adolescents overindulged in games, 4. the content elements of counseling for adolescents overindulged in games. The conclusion of this study is as follows. First, the prevention model of game overindulgence requires ecological understanding about adolescents overindulged in games and therefore needs to be started from understanding of the process of overindulgence in games and the related environmental factors. Second, it was proved that the prevention model was the process driven by interaction among environmental factors around adolescents, which are parents, schools, and a game itself. Finally, the study showed counselors for adolescents overindulged in games should be equipped with professional qualification and cultivating specialists should also be required.