Introduction: Problematic usage of the internet (PUI) is an umbrella term for a range of uncontrolled, excessive, and potentially harmful online behaviors. Recently, numerous studies have examined the potential of mindfulness programs (MPs) for reducing PUI. We conducted a comprehensive systematic review and meta-analysis in this emerging field. Methods: We searched eight databases from inception to October 18, 2022, with no language restrictions. We included randomized controlled trials (RCTs) and nonrandomized trials (NRTs). The primary outcome was change in self-reported PUI, the secondary outcome was change in screen time. Results: Of 3,473 identified records, 19 RCTs and 20 NRTs with a total of 1,549 participants were included. Participation in an MP was associated with large reductions in PUI in between-group analysis in RCTs (k 5 19; g 5
1.67; 95% CI
2.15,
1.19) and in within-group pre-post analysis in all studies (k 5 35; g 5
1.67; 95% CI
1.99,
1.36). Screen time showed a medium reduction in within-group pre-post analysis (k 5 10; g 5
0.65; 95% CI
0.90,
0.41). The effects for PUI remained significant in a series of sensitivity analyses, such as excluding low quality studies, excluding outliers, adjusting for publication bias, or using follow-up data. Heterogeneity between studies was high and the overall quality of evidence was rated low. Discussion and conclusions: MPs are probably effective in reducing PUI and might be effective in reducing screen time. Shortcomings in the quality of evidence highlight the need for high-quality controlled trials with long-term follow-ups to confirm results.  Kulcsszavak: problematic internet use, internet use disorder, mindfulness, social network, gaming, screen time