IntroductionInternet use disorder (IUD) is on the rise and is associated with detrimental health consequences. Growing evidence suggests that mindfulness—either as a trait or cultivated in mindfulness-based programmes (MBPs)—is promising in preventing and treating IUD. With this systematic review and meta-analysis, we will examine (1) the association between trait mindfulness (TM) and IUD and (2) the effectiveness of MBPs in reducing IUD.Methods and analysisIn October 2022, we will screen Medline, PsycINFO, PSYINDEX, CINAHL, Web of Science, and the Cochrane Register of Controlled Trials without language or publication date restrictions. We will conduct backward and forward citation searches of included studies and relevant reviews. We will include studies that evaluate either (1) the association between TM and IUD or (2) the effectiveness of MBPs in reducing IUD. Two reviewers will independently screen records, select and extract data, and rate the risk of bias. In total, we will conduct three meta-analyses: a first meta-analysis will be on the correlation between TM and IUD, a second meta-analysis will be on between-group data examining the effectiveness of MBPs in reducing IUD in randomised controlled trials (RCTs), and a third meta-analysis will be on within-group pre-postdata examining the effectiveness of MBPs in reducing IUD in all kinds of intervention studies. For the second and third meta-analyses, the primary outcome will be changes in IUD. We will explore moderators and sources of between-study heterogeneity and pursue a narrative synthesis of results. We will use the Grading of Recommendations Assessment, Development and Evaluation system to assess the overall quality of evidence across intervention studies.Ethics and disseminationEthics approval is not required. Results will be published in a peer-reviewed journal and presented at (inter)national conferences.PROSPERO registration numberCRD42022350071.