Background: As incarcerated populations report significantly higher prevalence rates for psychological distress than community populations, it is important to have an evidence-based perspective on what reduces psychological distress among people in prison or jail. Aims: To examine effects of mindfulness-based interventions (MBIs) on psychological distress, including anxiety, depressive symptoms, stress and overall psychological distress, and on mindfulness in incarcerated populations. Methods: This systematic review and meta-analysis of randomised controlled trials (RCTs) involved a comprehensive search within the PubMed, CINAHL, PsycINFO, and SCOPUS databases to identify relevant RCTs. The quality of the included RCTs was assessed using the Cochrane Collaboration risk of bias tool. Depending on I2 statistic values for heterogeneity, either a random effects model or fixed effects model was used. Subgroup analyses for each outcome were conducted to see whether effects differed when compared MBIs to active control groups, provided with other comparable interventions, or passive control groups, provided with no intervention (i.e., treatment as usual [TAU] control groups or waiting list controls). Results: Thirteen RCTs met the eligibility criteria. Meta-analyses showed moderate effects of MBIs on depressive symptoms and overall psychological distress, large effects on stress, and small effects on anxiety and mindfulness. The overall risk of bias across studies was unclear. Fewer studies were conducted to compare effects of MBIs to other interventions than TAU. Conclusions: Future high-quality studies comparing MBIs to other active interventions are needed to understand better whether the former are comparable or superior to other evidence-based treatments in decreasing distress and improving mindfulness in incarcerated populations and/or in which circumstances one may be preferable to the other.