As adolescents are in a crucial developmental period, they are more susceptible than adults to Internet gaming disorder (IGD). The dual-system model proposed by Casey, Jones, and Hare (2008) emphasized the equal importance of reward-seeking and cognitive control systems in accounting for adolescents' risky behaviors. Considering that no study has simultaneously examined reward seeking (loss aversion, i.e., loss sensitivity relative to gain sensitivity) and cognitive control (inhibitory control) in IGD, this study aimed to investigate loss aversion and inhibitory control in the same IGD adolescent population. Forty five adolescent patients with IGD and 43 matched healthy control participants completed a mixed gambles task and a stop-signal task to measure loss aversion and inhibitory control, respectively. Two main findings were identified in this study. First, the IGD participants showed concurrent reduced loss aversion and inhibitory control, suggesting that differences in both systems serve as behavioral markers of IGD in adolescents. Second, the IGD participants were categorized into 2 distinct subtypes based on differences in loss aversion and inhibitory control, which implies specific therapies for specific subtypes of IGD adolescents. Therefore, this study extends the application of the dual-system model to explain adolescents' excessive Internet gaming behavior.