Mental health problems are a growing and significant issue in the Australian education system. Research has suggested that resilience can be learned and that schools can play an important role in developing resilient skills among youth; however, rigorous evaluation of interventions promoting resilience is limited. Aims: As martial arts training has been found to have psychological benefits such as increased confidence and self-esteem, this study investigated whether a 10-week martial arts training programme was an efficacious sports-based mental health intervention that promoted resilience in secondary school students. Sample: Two hundred and eighty-three secondary school students (age range 12–14 years) participated in the study. Methods: The study examined the effects of martial arts training on participants’ resilience by delivering a 10-week martial arts-based intervention in secondary school settings. The intervention was evaluated using quantitative methodology and an experimental research design using a randomized controlled trial which measured participant responses at baseline, post-intervention, and follow-up. Results: The study found that the martial arts-based intervention had a significantly positive effect on developing students’ resilience. This was especially apparent when the intervention and control group’s mean resilience outcomes were compared. Resilience outcomes appeared to be stronger immediately following the intervention compared with 12-week follow-up. Conclusions: Given the prevalence of mental illness among Australian youth, the current study provides robust evidence that students’ resilience can be improved using martial arts-based interventions delivered in school settings. Trial Registration: Australian New Zealand Clinical Trials Register ACTRN12618001405202. Registered 21 August 2018.