With the rise of digital devices, gaming has become both a pastime and part of the culture for young people. Teenagers use games to communicate, enjoy leisure time, and relieve stress. However, the maladaptive use of gaming can lead to difficulties in adolescents’ daily lives and school adjustment. Increasing adolescents’ self-regulation competencies can improve maladaptive gaming behaviors and help them use gaming adaptively. Therefore, this study examined the moderating effect of self-regulation on the impact of adolescent gaming behavior on school adjustment. This study considered 359 adolescent participants in South Korea. Data were analyzed using hierarchical regression to test the moderating effect. The results indicated that adolescents’ adaptive use of games significantly increased school adjustment. Self-regulation significantly moderated the negative effects of the maladaptive use of games on school adjustment. Furthermore, the results revealed that the groups with highly adaptive and maladaptive use of games had high school adjustment but low self-regulation, indicating that they required active intervention.