Although mindfulness-based interventions (MBIs) have been shown to be effective in treating several psychological difficulties, to date, no review has systematically examined their effectiveness in treating or preventing suicide. The goals of the present study were to (1) evaluate the effectiveness of MBIs in treating suicide and (2) understand how individual characteristics and characteristics of MBIs influence treatment outcomes through a systematic meta-analysis. A search of PubMed, MEDLINE, PsychINFO, and ProQuest Dissertations and Theses was conducted in February 2019. A total of 12 publications (13 studies, n = 627) were included. MBIs demonstrated significant moderate effects on suicidal ideation in pre-post studies and small effects in controlled studies. In addition, MBIs demonstrated significant moderate effects in both samples of individuals with histories of depression and histories of suicidal ideation or attempts. Moreover, MBIs led to clinically significant reductions in suicidal ideation and depression. Female participants, older samples, and longer treatments showed greater treatment effects, although these relationships were weak. Results suggest that MBIs may be promising treatments for suicidal ideation; however, more research is needed to establish the effects of these treatments as well as the mechanisms through which MBIs reduce suicide.