--- - |2+ Abstract Objective While there is sufficient research and clinical evidence to support the inclusion of gaming disorder in the latest revision of the International Classification of Diseases (ICD‐11), relatively little is known about the effectiveness of first‐line psychological treatment for gaming disorder or Internet gaming disorder (IGD) as it is listed in the DSM‐5. This systematic review employed meta‐analytic techniques to determine the effectiveness of cognitive‐behavioral therapy (CBT) for IGD on four key outcomes: IGD symptoms, anxiety, depression, and time spent gaming. Method A database search identified 12 independent CBT studies. Effect size estimates (Hedges' g) with associated confidence intervals, prediction intervals and p values, for each pre‐post treatment outcome, were calculated. Study reporting quality was evaluated in accordance with the Consolidated Standards of Reporting Trials (CONSORT) guidelines. Subgroup and moderator analyses were undertaken to investigate potential sources of heterogeneity. Results CBT demonstrated high efficacy in reducing IGD symptoms (g=.92, [0.50,1.34]) and depression (g=.80, [0.21,1.38]) and showed moderate efficacy in reducing anxiety (g=.55, [0.17,0.93]) at post‐test. There was insufficient power to determine whether CBT was capable of reducing time spent gaming. Treatment gains at follow‐up were non‐significant across the four treatment outcomes. Conclusions The pooled findings suggest that CBT for IGD is an effective short‐term intervention for reducing IGD and depressive symptoms. However, the effectiveness of CBT for reducing actual time spent gaming was unclear. Given the limitations of this evidence base, there is a need for more rigorous studies to determine the potential long‐term benefits of CBT for IGD. - Clinical Psychology & Psychotherapy, Volume 0, Issue ja, -Not available-.