Developmental theories posit that immature cognitive control and excessive reward-seeking capacities may be a risk factor for addictive behaviors during adolescence, but the control and reward capacities have rarely been assessed experimentally in adolescents with Internet gaming disorder (IGD) simultaneously. This electrophysiological study examined inhibitory control and reward processing in adolescents with IGD during a go/no-go task and a gambling task. Behaviorally, the adolescents with IGD exhibited lower inhibitory control, as measured by the accuracy of no-go trials, and more risk seeking, as measured by the proportion of risky choices, than did the controls. Compared with the controls, the adolescents with IGD exhibited decreased no-go P3 and blunted feedback-related negativity (FRN) amplitudes following gains (gain FRN) but not losses. Thus, IGD in adolescents is potentially driven by dysfunction of the control system and the approach system rather than the avoidance system, supporting the neurobiological model of adolescent development.