Mental health issues are of increasing public concern, however are often untreated for a variety of reasons. While limited, the research examining the relationship between mental health and martial arts training is generally positive. This systematic review and meta-analysis explored whether martial arts training may be an efficacious sports-based mental health intervention. Design: The meta-analysis used a random effects model and examined three mental health outcomes: wellbeing, internalising mental health, and aggression. Data sources: During January to July 2018 the following electronic databases were searched: CENTRAL, EBSCO, Embase, ERIC, MEDLINE, PUBMED, and ScienceDirect. Eligibility criteria: Eligibility criteria included: (1) martial arts was examined as an intervention or activity resulting in a psychological outcome, (2) the study reported descriptive quantitative results measured using standardised scales that compared results between groups and (3) studies were published as full-length articles in peer reviewed scientific or medical journals. Results: More than 500,000 citations were identified and screened to determine eligibility. Data was extracted from 14 eligible studies. Martial arts training had a significant but small positive effect on wellbeing (d = 0.346, 95% CI = 0.106 to 0.585, I2 = 59.51%) and a medium effect on internalising mental health (d = 0.620, 95% CI = 0.006 to 1.23, I2 = 84.84%). Martial arts training had a minimal non-significant positive effect in reducing aggression (d = 0.022, 95% CI = −0.191 to 0.236, I2 = 58.12%). Summary/conclusion: Whilst there is considerable variance across the studies included in the meta-analyses, there is support for martial arts training as an efficacious sports-based mental health intervention for improving wellbeing and reducing symptoms associated with internalising mental health.