Objectives <p>Mindfulness-based programs (MBPs) are promising evidence-based interventions to mitigate the mental health crisis amongst young adults. This meta-analysis investigated MBPs’ impact on mental health outcomes and facets of mindfulness to inform the design of precise, evidence-based interventions addressing young adults' needs.</p> Methods <p>Systematic searches were conducted using PubMed, MEDLINE, PsycINFO, and Web of Science for RCTs involving young adults (18–30 years). Three-level random-effects models were used to examine the pre- to post-treatment effects of MBPs compared to a control group on the following outcomes: anxiety, depression, stress, distress, positive affect, negative affect, mindfulness, and its facets; observing, describing, acting with awareness, nonjudging, and nonreactivity. Mixed meta-regression models and subgroup analyses were used to explore study, sample, and intervention characteristics. RoB 2.0 and GRADE were used to assess quality.</p> Results <p>Across 132 eligible studies (<i>N</i> = 6883 participants and <i>N</i> = 6910 controls), MBPs significantly improved both mental health and mindfulness outcomes (<i>g</i>-values &gt; 0.29) with substantial residual heterogeneity. The certainty of evidence ranged from moderate to low due to issues with risk of bias and likely publication bias in certain outcomes. Subgroup analyses indicated that multimodal mindfulness programs, MBCT, MBSR, and their derivations were effective for mental health outcomes. Most reliable improvements were identified in monitoring-focused mindfulness facets. Intervention and study characteristics explained 6–15% of heterogeneity.</p> Conclusions <p>MBPs are useful tools to enhance mental health and facets of mindfulness in young adults. The significant residual heterogeneity necessitates further examination of the features of face-to-face MBPs and multimodal programmes. </p> Pre-registration <p>The protocol was registered with PROSPERO (CRD42024575536).</p>